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Accelerated Long-term Forgetting (ALF) is a memory deficit characterised by normal retention up to relatively short intervals (e.g., minutes, hours) with increased forgetting over longer periods (e.g., days, weeks). ALF is often underestimated due to a lack of common memory assessments beyond 30-60 min. The purpose of this review was to provide an overview of ALF occurrence in neurodegenerative disorders, evaluating whether it can be considered a cognitive deficit useful for diagnosing and monitoring patients. We included 19 experimental studies that investigated ALF in neurodegenerative disorders. Most papers were focused on Alzheimer's disease (AD) dementia and related forms of cognitive decline (Mild Cognitive Impairment, Subjective Cognitive decline, Pre-symptomatic subjects at risk of AD dementia). The major finding of the present work concerns the presence of ALF in very early forms of cognitive decline related to AD. These findings, supporting the hypothesis that ALF is a subtle and undetected hallmark of pre-clinical AD, highlights the importance of investigating forgetting over a longer period and devising standardised measures to be included in clinical practice., Competing Interests: Conflict of interest The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Apathy symptoms include different dimensions: cognitive (C), emotional-affective (E-Aff) and auto-activation; they have been related to dysfunctions of the dorsolateral, orbito-basal prefrontal cortex and the subcortical frontal connections to the basal ganglia, respectively. In Alzheimer's disease (AD), an association has been found between apathy severity and both executive deficits and atrophy of the dorso-lateral prefrontal cortex; however, it is not clear whether these associations concern only the cognitive aspects of apathy. Furthermore, whether there is an association in AD between E-aff apathy and theory of mind (ToM),the cognitive functions subsumed by the orbito-basal prefrontal cortex, has not been investigated. Aim of the study was to investigate the relationship between C, E-Aff and auto-activation apathy and performance on tasks investigating executive and ToM cognitive functions in AD. For this purpose, 20 AD patients with apathy and 20 matched controls were submitted to an executive and ToM neuropsychological assessment. Apathy was assessed with a weekly diary (ApD) created specifically to assist caregivers in quantifying the C, E-Aff and auto-activation symptomatology of apathy. Correlational analyses showed that AD patients' scores on the Modified Card Sorting Test (MCST) and Emotion Attribution tasks were correlated with most ApD scores. However, regression analyses showed that C diary scores were predicted by MCST performance, E-Aff diary scores by performance on the E-Attribution task and ApD scores measuring auto-activation apathy were predicted by both the MCST and the Emotion Attribution scores. These results confirm the co-occurrence of apathy and executive-function deficits in AD and suggest a specific association between AD patients' executive deficits and the cognitive component of apathy. Furthermore, they document, for the first time, an association between poor performance on tests assessing ToM abilities and the emotional-affective component of apathy in AD patients. Finally, these results are in line with the view that auto-activation apathy reflects the sum of emotional and cognitive processing deficits., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Apathy is frequently reported in individuals with Parkinson's disease (PD) and is hypothesized to be associated with frontal-striatal related cognitive functions. Available data, however, do not provide univocal results. Moreover, this relationship has been poorly investigated in PD patients with mild cognitive impairment (MCI). This study was aimed at investigating the association between severity of apathy of PD patients and their performance on neuropsychological tests investigating executive abilities. Individuals with PD (i.e., with and without MCI) and healthy controls (HCs) were administered a neuropsychological test battery that investigated episodic memory, language, short-term memory and attention, visual-spatial abilities and executive functions. Subjects were also administered additional neuropsychological tests to evaluate the different executive subcomponents (i.e., planning/abstract reasoning, self-monitoring/response inhibition, working memory, shifting and fluency). The Apathy Evaluation Scale (AES) was administered to assess apathy severity. Linear regression analyses were applied to the data; results showed that in the PD group with MCI, the best cognitive factor associated to the AES score was patients' scores on the executive tests and, in particular, their scores on tests examining planning/abstract reasoning. By contrast, in the PD group without MCI, the cognitive performance was not significantly associated to apathy severity. Findings of the study document a specific association between reduced efficiency of the executive system and apathy severity in individuals with PD and MCI. This association indirectly supports the hypothesis of a relationship between motivational disorders and dysregulation of the activity of the frontal-striatal networks in PD patients., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Dual-process theories of recognition memory sustain that recollection and familiarity reflect different mnemonic processes and rely on separate neural substrates that are located primarily in the medial temporal lobe (MTL). Aggleton and Brown's model (1999) assumes that this distinction extends to other brain regions, including the thalamus, and that both recognition memory processes interact with the prefrontal cortex (PFC). Nevertheless, it is still unclear whether recollection and familiarity are subtended by separate prefrontal regions. Here we provided a review of the literature that first focused on functional magnetic resonance imaging studies that adopted the Remember/Know method and reported recollection- and familiarity-based activity in the PFC. There is evidence that functional activations are differently located within the lateral (i.e., along the dorso-ventral axis), medial (i.e., along the rostro-caudal axis) and anterior (i.e., along the medio-lateral axis) prefrontal surfaces according to whether they are recollection- or familiarity-related. Overall, the findings we summarise suggest that recollection and familiarity are qualitatively different processes and rely on distinct neural pathways even outside the MTL., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Episodic autobiographical memory (ABM) has been found to be impaired from the early stage of Alzheimer's disease (AD). Previous works have focused on how ABM decreases over the lifespan, but no study has deeply investigated whether the extent of episodic autobiographical amnesia is mediated by the retrieval frequency of the episodic trace itself. The aim of the present study was to determine whether the frequency of trace retrieval has an effect on the quality of autobiographical incidents recall and whether the extent of this contribution changes over time. For this purpose, the episodic component of ABM was assessed in patients in the early stage of AD through a questionnaire which allowed evaluating memory of past personal incidents as a function of both their age of acquisition and retrieval frequency. We found that both AD patients and healthy controls took advantage of greater retrieval frequency across all time segments, because of their better memory performance on frequently retrieved episodes than less frequently retrieved ones. Although in the AD group the retrieval frequency effect (i.e., higher scores on the episodes rated as more frequently retrieved) was found in all time segments, the extent of its beneficial effect on memory performance was temporally-graded and inversely related to the time course. Our findings provide new evidence that the combined action of both age of memory and retrieval frequency could provide a valuable framework for predicting patterns of ABM loss, at least in early AD patients. In line with the Multiple Trace Theory, we speculated that retrieval frequency protects episodic trace recall against hippocampal damage by reinforcing the neural representation of personal context-rich memories, which consequently are easier to access and recall. Furthermore, the age of memory should change the amplitude of this beneficial effect as a function of the remoteness of the trace., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This paper provides a focused review of the literature on semantic impairment in semantic dementia (SD) and Alzheimer's disease (AD). An attempt is made to interpret the most relevant phenomena in the light of a new model of semantic memory. This model comprises a language-based component (disrupted in SD and AD), which supports our ability to establish reliable token vs. type relationships in the service of propositional thinking, and a philogenetically older sensorimotor component, which is needed to categorize our environment in a more implicit way. Extant neuropsychological models of semantic memory are also reviewed and compared with the new model in terms of their ability to explain the observed phenomena and to deal with the problem of establishing token vs. type relationships starting from inconsistent cross modal input representations and arbitrary category boundaries., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Recollection and familiarity are two distinct forms of recognition memory that differ in terms of the associative richness of the memory experience. In recollection, exposure to a previously encountered item cues the recollection of a number of contextual, temporal and other associative information. In the case of familiarity, instead, the item is recognized as previously encountered, but it does not cue any associative information. According to the dual-process theory, the memory processes that underlie recollection and familiarity are qualitatively different and this distinction is reflected in the existence of different neural substrates underlying the two processes. Thus far, research has primarily focused on distinct regions of the medial temporal lobe as implicated mostly in recollection (hippocampus) or familiarity (perirhinal cortex). Aggleton and Brown (1999) suggested extending the neuroanatomical distinction to other cortical and subcortical areas of the brain, including the thalamus. In particular, they proposed the existence of two reciprocally independent neural circuits for recollection and familiarity. The former would include the hippocampus, the fornix, the mammillary bodies and the anterior thalamic nuclei. The second would involve the mesial magnocellular portion of the mediodorsal nucleus connected to the perirhinal cortex through the ventroamygdalofugal pathway. Here we review neuropsychological evidence in experimental animals and brain-damaged individuals and functional neuroimaging evidence in healthy humans that supports Aggleton and Brown's model at the level of the thalamus. The evidence substantially supports the functional relationship between recollection processes and integrity of the thalamic anterior nuclei. Additional evidence, not predicted by the model, has been provided in favour of the reliance of recollection on the integrity of the lateral portion (parvocellular) of the mediodoral nucleus. Finally, there is sparse and controversial evidence in support of the reliance of familiarity on the integrity of the mesial portion of the mediodorsal nucleus, possibly due to neuroimaging methodological limits which did not satisfactorily distinguish between the medial and lateral portions of the mediodorsal nucleus., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Recent studies have suggested that medial (medBA10) and lateral (latBA10) portions of the Brodmann area 10 subserve respectively stimulus-oriented (SO) and stimulus-independent (SI) attending during prospective memory (PM) tasks. We investigated this dissociation by manipulating the saliency (SO) and the memory load (SI) of PM cues. Sixteen healthy subjects participated to a functional imaging protocol with a 2×2×2 experimental design, including the factors: task (ongoing target vs. PM cue), Saliency (high vs. low; with targets/cues either embedded or standing out from distracters), and memory load (high vs. low; with 1 or 4 possible PM targets). We localized the medBA10 and latBA10 by means of a localizer task. In medBA10 we found a significant main effects of high Saliency and low memory load; whereas in the left latBA10, we found a significant task×load interaction, with maximal activation for PM cues presented in the high load condition. These results are in agreement with the gateway hypothesis: during a PM task medBA10 biases attention toward external salient stimuli, SO attending, while latBA10 biases attention toward internal mnemonic representations, SI attending. Additional whole-brain analyses highlighted activation of other areas besides BA10, consistent with recent proposals that emphasise the role of distributed networks during PM performance., (© 2013 Published by Elsevier Ltd.)

Evidence shows that amnesic patients are able to categorize new exemplars drawn from the same prototype as in previously encountered items. It is still unclear, however, whether this ability is due to a spared implicit learning system or residual explicit memory and/or working memory resources. In this study, we used a new paradigm devised expressly to rule out any possible contribution of episodic and working memory in performing a prototype distortion task. We enrolled patients with amnesic MCI and Normal Controls. Our paradigm consisted of a study phase and a test phase; two-thirds of the participants performed the study phase and all participants performed the test phase. In the study phase, participants had to judge how pleasant morphed faces, drawn from a single prototype, seemed to them. Half of the participants were shown faces drawn from the A-prototype and half from the B-prototype. A- and B-faces were opposite in a morphing space with a neutral human face at the center. In the test phase, participants had to judge the regularity of faces they had never seen before. Three different types of faces were shown in the test phase, that is, A-, B-, or neutral-faces. We expected that implicit learning of the category boundaries would lead to a category-specific increase in perceived regularity. The results confirmed our predictions. In fact, trained subjects (compared with subjects who did not undergo the study phase) assigned higher regularity scores to new faces drawn from the same prototype as the faces seen during training, and they gave lower regularity scores to new faces drawn from the opposite prototype. This effect was super imposable across subjects' groups., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The contribution of the thalamus to the functioning of prospective memory (PM) is currently unknown. Here we report an experimental investigation of the performance of two patients with bilateral infarcts in the anterior-mesial regions of the thalami on an event-based PM paradigm. One patient, G.P., had a pervasive declarative memory impairment but no significant executive deficit. The other patient, R.F., had a memory deficit limited to verbal material with associated behavioral abnormalities (inertia and apathy); she performed poorly on tests of executive functions. Although both patients performed poorly on the PM task, a qualitative analysis of performance revealed different mechanisms at the base of their impaired PM. G.P. had reduced declarative memory for target words compared with normal controls; but, unforgotten words were normally able to elicit his recall of the prospective intention. Conversely, R.F.'s declarative memory for target words was as accurate as that of normal controls, but she presented a dramatically reduced ratio between the number of target words she recalled and the number of times she activated the prospective intention on the PM task, suggesting that her deficit consisted of difficulty in activating the intention despite normal declarative memory for the target events. In conclusion, results of the present study demonstrate that thalamic structures have an important role in PM processes. They also document that damage to the anterior-mesial regions of the thalami affects PM abilities by two different mechanisms, respectively based on the relative disruption of declarative memory or executive processes functioning, which, in turn, is related to the specific intrathalamic structures involved by the lesions. Indeed, while G.P.'s pervasive declarative memory deficit was underlain by bilateral involvement of the mammillo-thalamic tract, R.F.'s executive and behavioral abnormalities were likely related to bilateral damage of the midline, intralaminar, and medio-dorsal nuclei., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Prospective memory (PM) deficits have recently been documented in individuals with amnestic mild cognitive impairment (aMCI). In this paper, we investigated whether these deficits are due to the failure of retrospective memory processes. We also examined the role played by attentional/executive processes in PM functioning. We enrolled 24 individuals with aMCI and 24 healthy controls (NCs). In the PM procedure, we manipulated both the memory load of the retrospective component of the PM task and the complexity of the ongoing task in a 2 × 2 experimental design. Sequences of four words were presented. Participants had to repeat the sequence in the same order (low attentional demand condition) or in the reverse order (high attentional demand condition). When a target word appeared in the sequence, participants had to press a button on the keyboard (PM task). Target words could be one (low memory load condition) or four (high memory load condition) in different blocks. MCI participants obtained lower PM scores than NCs in all four experimental conditions. However, they recalled the target words less accurately than NCs only in one four-word condition. Finally, the executive demand of the ongoing task did not significantly affect the PM performance of aMCI individuals. Our findings confirm that PM is severely impaired in individuals with aMCI. Moreover, a failure of retrospective memory processes does not seem to fully account for the poor PM performance in aMCI individuals. Finally, the finding that in these individuals, a deficit in executive control cannot be claimed as the main responsible for the observed PM impairment could suggest the involvement of automatic-reflexive processes., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Most models of visual object recognition assume that items belonging to known categories are represented in long-term memory in terms of both structural descriptions and semantic representations. The former specify the visual appearance of category members and the latter allow recognising them as meaningful objects. Nevertheless, the format of these two kinds of representations and their relationships are still a matter of debate. Recently, the independence of structural and semantic representations has been questioned on the basis of the finding of an impaired performance of subjects suffering from semantic dementia on the object decision task, which was originally devised to tap the structural description system. In the present case study of a patient with semantic dementia, we provide data supporting the independence of these two systems. Our results allowed us to better qualify the content and format of structural descriptions in terms of purely geometric non-verbalizable information, specifying the appearance of exemplars at a rather coarse level of categorisation., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Semantic priming paradigms have been used to investigate semantic knowledge in patients with Alzheimer's disease (AD). While priming effects produced by prime-target pairs with associative relatedness reflect processes at both lexical and semantic levels, priming effects produced by words that are semantically related but not associated should reflect only semantic activation processes. This study was aimed at further investigating automatic semantic priming effects in AD patients when semantically related concepts with little to no lexical association are used. Twenty patients with mild to moderate AD and 20 matched controls (NCs) performed a lexical decision task on 30 concept pairs (15 in the living and 15 in the non-living domain) in an automatic semantic priming paradigm. In order to investigate the relationship between priming alteration and semantic damage, we chose concepts from a database. This allowed us to quantify semantic indexes relative to the structural representation at the feature level. No priming was found in NCs or mild AD patients, probably because feature similarity was insufficient in the concept pairs used. Similar to the hyperpriming observed in previous studies, the appearance of priming in the moderate AD group suggests early semantic damage in which attribute knowledge is partially affected. Furthermore, the finding that priming was predicted by the level of sharing (in the semantic system) of features common to the two concepts in the pairs indicates that the level of redundancy of attribute information is the main factor responsible for resiliency to neurological damage in AD., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

In humans lacunar infarcts in the mesial and anterior regions of the thalami are frequently associated with amnesic syndromes. In this review paper, we scrutinized 41 papers published between 1983 and 2009 that provided data on a total of 83 patients with the critical ischemic lesions (i.e. 17 patients with right-sided lesions, 25 with left-sided lesions and 41 with bilateral lesions). We aimed to find answers to the following questions concerning the vascular thalamic amnesia syndrome: (i) Which qualitative pattern of memory impairment (and associated cognitive and behavioral deficits) do these patients present? (ii) Which lesioned intrathalamic structures are primarily responsible for the amnesic syndrome? (iii) Are the recollection and familiarity components of declarative memory underlain by the same or by different thalamic structures? Results of the review indicate that, similar to patients with amnesic syndromes due to mesio-temporal lobe damage, patients with vascular thalamic amnesia display a prevalent deficit of declarative anterograde long-term memory, a less consistent deficit of declarative retrograde long-term memory and substantially spared short-term and implicit memory. Unlike mesio-temporal lobe patients, however, vascular thalamic amnesics often present dysexecutive and behavioral deficits similar to those observed in patients with frontal damage. The presence of an amnesic syndrome in patients with thalamic lacunar infarcts is strongly predicted by involvement of the mammillo-thalamic tract, which connects the anterior nuclei complex to the hippocampus proper via the fornix and the mammillary bodies. Finally, data reported in a few single cases provide support for the hypothesis that thalamic regions connected to distinct areas of the mesio-temporal lobe play differential roles in recollection and familiarity processes. The mammillo-thalamic tract/anterior nuclei axis seems primarily implicated in recollective processes, whereas the ventroamygdalofugal pathway/medio-dorsal axis primarily underlies familiarity processes., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

There is now a large body of evidence suggesting that color and photographic detail exert an effect on recognition of visually presented familiar objects. However, an unresolved issue is whether these factors act at the visual, the semantic or lexical level of the recognition process. In the present study, we investigated this issue by having Alzheimer's patients and normal controls name figures in four presentation displays (PDs): black and white and colored line drawings, and black and white and color photographs. We also collected image agreement (IA) values (a measure of the extent to which the presented figure matches the stored structural description of the depicted object) for the same stimuli and compared the effects of PD on IA and naming accuracy. Our results suggest that color acts on naming by assisting semantic processing of the stimuli to be recognized; by contrast, photographic detail seems to benefit visual processing by increasing IA., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

Very few studies have investigated the relationship between dopaminergic therapy and working memory (WM) functioning in Parkinson's disease (PD) patients. The aim of the present study was to explore the effects of pharmacological treatment with pergolide (a D1+D2 receptor agonist) and pramipexole (a D2+D3 receptor agonist) on performance in visual-spatial, visual-object, and verbal WM tasks in PD patients. Participants included 19 "de novo" PD patients and 13 healthy controls (HC). The experimental task consisted of an n-back paradigm with verbal, visual-object, or visual-spatial stimuli. PD patients performed the task twice: after 18-24 h of therapy wash-out and after administration of pergolide (nine patients) or pramipexole (ten patients). HCs performed the task only once, without drug administration. Depending on how they performed in the "Off" and "On" therapy conditions, the nine PD patients each were classified into groups of low performers (i.e., performance on the n-back paradigm was below the median value of the experimental sample) and high performers (i.e., performance was above the median value). One PD patient was excluded from the analysis because his performance pattern clearly revealed that he was an outlier. In the low performer PD patients, administration of both pergolide and pramipexole improved accuracy on all WM tasks. No effect of the drugs was found in the high performer patients. The results of the present study show that stimulation of dopaminergic receptors improves high-level WM processes in PD patients, possibly by modulating activity in frontal-striatal circuits.

The basal ganglia have been associated with temporal processing in ranges of milliseconds and seconds. However, results from PD patient studies are elusive. Time perception in these patients has been tested with different approaches including repetitive movement tasks (i.e. finger tapping) and cognitive tasks (i.e. time reproduction), and both abnormal and normal performances have been reported for different time intervals. Furthermore, when PD patients were required to learn two target durations in the same session when they were off medication, they overestimated the short duration and underestimated the long duration in the seconds range. This pattern of temporal accuracy was described as a "migration effect" and was interpreted as a dysfunctional representation of memory for time (Malapani, C., Rakitin, B. C., Levy, R., Meck, W. H., Deweer, B., Dubois, B., et al. (1998). Coupled temporal memories in Parkinson's disease: A dopamine-related dysfunction. Journal of Cognitive Neuroscience, 10, 316-331). Here, we controlled the emergence of similar behaviour also during millisecond time processing in PD patients. A time reproduction task was employed in which subjects were required to estimate intervals in millisecond (500ms) and few second (2000ms) ranges. In the first experiment, these intervals were tested in the same session to verify whether the migration effect was present also between time intervals in different millisecond and few second ranges. In a second experiment, they were not intermingled but were tested in two separate sessions to verify whether abnormalities depended on a selective perceptual deficit of the time intervals tested (i.e. millisecond or second ranges). All experiments were performed in both off and on therapy conditions. Our results demonstrated that PD patients showed no deficits in time estimation for time intervals in either the millisecond or few second range when the different time intervals were tested in separate sessions. This negative finding was obtained in both on and off conditions. However, when the different ranges were tested in the same session, we found that PD patients were impaired selectively for time intervals in the seconds range. Our data seem to indicate that time processing in PD patients for time intervals spanning up to 2s is unimpaired and that abnormalities in such temporal scale may emerge only when patients have to deal with different durations, when timing involves further cognitive processes such as memory and attention.

Focal damage confined to the hippocampus may result in recognition deficits characterized by a dissociation between impaired recollection and preserved familiarity. Here, we report a single case of an amnesic patient with bilateral damage to the anterior part of the thalamus, who presented with a neuropsychological profile suggesting such a dissociation. We hypothesized that this focal damage involved the so-called Delay and Brion's circuit, which has been theorized to subserve episodic memory processes, but at a different anatomical level than in patients with hippocampal lesions. Using two independent experimental paradigms (remember/know and confidence receiver operating characteristics [ROC]) and recruiting a sex- and age-matched group of healthy controls, we demonstrated that this patient's recognition deficits were due to a selective impairment of recollection with a normal familiarity process. The patient underwent an ad hoc brain MRI study, and a quantitative analysis of his MR images was performed. Tissue damage extended bilaterally to the mammillo-thalamic tract, with complete preservation of the medio-dorsal thalamic nuclei. Our findings support the idea that the same functional specialization hypothesized for the different sub-regions of the mesial temporal lobe might also extend to the thalamus. This case will be discussed in light of its implications in support of recent theories, which regard recollection and familiarity as independent processes associated with different neural circuits.

A category-specific naming effect penalizing living things has often been reported in patients suffering from Alzheimer's disease (AD) and in other brain damaged populations, while the opposite dissociation (i.e., lower accuracy in naming nonliving than living things) is much rarer. In this study, we investigated whether the use of line drawings (rather than color photographs) in picture-naming tasks could be a relevant factor in the emergence of a category effect penalizing living things and found evidence in favor of this hypothesis. We administered the same naming tasks comprising living and nonliving items to 10 subjects suffering from AD and 10 normal controls. Once the stimuli were line drawings and once color photographs. A reliable Group x Semantic domain interaction, indicating a disproportionate impairment for living things in the AD group, was only found when line drawings were presented. Results are discussed with reference to two competing approaches to category-specificity in brain damaged people. One assumes that category effects are due to the differential involvement of dedicated neural subsystems, the other emphasizes the role of cross domains imbalances in processing demands. We conclude that our findings lead support to the latter approach.

We report the case of C.L., an 8-year-old child who, following the surgical removal of an ependymoma from the left cerebral ventricle at the age of 4 years, developed significant difficulties in retaining day-to-day events and information. A thorough neuropsychological analysis documented in C.L. a severe anterograde amnesic syndrome, characterised by normal short-term memory, but poor performance on episodic long-term memory tests. In particular, C.L. demonstrated virtually no ability to recollect new verbal information several minutes after the presentation. As for semantic memory, C.L. demonstrated general semantic competencies, which, depending on the test, ranged from the level of a 6-year-old girl to a level corresponding to her actual chronological age. Finding a patient who, despite being severely impaired in the ability to recollect new episodic memories, still demonstrates at least partially preserved abilities to acquire new semantic knowledge suggests that neural circuits implicated in the memorisation of autobiographical events and factual information do not overlap completely. This case is examined in the light of growing literature concerned with the dissociation between episodic and semantic memory in childhood amnesia.

A semantic battery comprising items from living and nonliving categories was administered to a sample of subjects suffering from probable Alzheimer's type dementia (n=20). The results were analyzed to test the role of semantic distance in predicting group accuracy and its possible causal link with the phenomenon of a category-specific deficit for living things in the experimental population. Our findings confirm a category effect favoring nonliving items (over and above the role of confounding variables) in patients with Alzheimer's disease and support the major role of an imbalance of semantic distance in the testing material in the genesis of this phenomenon.

In this paper, we describe a patient (LI) suffering from semantic dementia who showed a category-specific naming impairment for living things over and above the effects of several nonsemantic confounding variables. We investigated the characteristics of LI's impairment to address the following three issues raised in three different accounts of category-specific impairments: (i) the role of an imbalance in the loss of sensory compared to nonsensory features (assumed by the Sensory Functional Theory [Warrington, E. K., & Shallice, T. (1984). Category-specific semantic impairments. Brain, 107, 829-859]); (ii) the role of cross domain differences in Feature Correlation (assumed by the Conceptual Structure Account [Moss, H., Tyler, L. K., & Devlin, J. T. (2002). The emergence of category-specific deficits in a distributed semantic system. In: E. M. E. Forde & G. W. Humphreys (Eds.), Category Specificity in Brain and Mind (pp. 115-147). New York: Psychology Press]); (iii) the role of semantic distance (proposed by Cree and McRae [Cree, G. S., & McRae, K. (2003). Analyzing the factors underlying the structure and computation of the meaning of chipmunk, cherry, chisel, cheese, and cello (and many other such concrete nouns). Journal of Experimental Psychology: General, 132, 163-201]). We found that semantic distance was the only factor causally linked to LI's poorer performance on living things. In fact, her naming performance was less accurate on items that had many semantic neighbours, which is typical of living things. On the contrary, a feature listing task revealed that the features available to LI were not predicted by their level of correlation, as expected by the Conceptual Structure Account. Finally, at variance with the Sensory Functional Theory, although LI quoted sensory features less accurately than nonsensory ones, this did not give rise to a disproportionate loss of semantic features in the living domain.

Recognition memory performance reflects two distinct processes or types of memory referred to as recollection and familiarity. According to theoretical claims about the two types of memory, single item and associative recognition tasks can be used as an experimental method to distinguish recollection and familiarity processes. Associative recognition decisions can be used as an index of recollection while memory for single items is mostly based on familiarity judgement. We employed this procedure to examine a possible dissociation in the memory performance of amnesic patients between spared single item and impaired associative recognition. Twelve amnesic patients, six with damage confined to the hippocampus proper, and six with damage elsewhere in the brain, were recruited for the present study. The findings showed that hippocampal amnesics exhibit relative sparing of single item learning but are consistently deficient in the learning of all kinds of between-item associations. These results are consistent with the view that hippocampal formation contributes differently to declarative tasks that require recollective or familiarity processes.

A positron emission tomography (PET) study was conducted to investigate the neurofunctional correlate of auditory within-modality and auditory-to-visual cross-modality stem completion priming. Compared to the auditory-to-auditory priming condition, cross-modality priming was associated with a significantly larger regional cerebral blood flow (rCBF) decrease at the boundary between left inferior temporal and fusiform gyri, brain regions previously associated with modality independent lexical retrieval and reading. Instead, within-modality auditory priming was associated with a bilateral pattern of prefrontal rCBF increase. This was likely the expression of more efficient access to output lexical representations and involuntary retrieval of the recent episode during which the just generated word had been encountered.

The breakdown of semantic knowledge relative to living and non-living categories was studied in patients with Alzheimer's disease (AD). The same living and non-living items were used in a semantic battery and in a semantic priming paradigm exploring automatic access to the semantic system. Although AD patients showed a semantic deficit on the intentional semantic battery, they demonstrated normal semantic facilitation on the priming task. In the AD group as a whole, the semantic impairment did not preferentially affect the living category either in the intentional or automatic condition. Instead, a prevalent deficit for the living category was found in three AD patients (14% of the group) on the intentional semantic tasks, but not on the automatic one. These findings support the view that the category effect may not be a generalised phenomenon in AD but may be restricted to a limited number of patients. The intentional/automatic dissociation of the semantic breakdown demonstrated by AD patients is discussed in relation to different theories regarding the organisation of semantic memory.

Several questions about category specificity associated with lexical-semantic deficits in Alzheimer's disease (AD) patients are still being debated. In this study, we enrolled 53 AD patients and 30 normal control subjects to investigate the following issues: Is category specificity consistently associated with AD? Do AD patients show both possible patterns of category specific impairment, i.e. selective impairment for either living things or artifacts? Is the direction of the category specific effect predictable as a function of disease severity? Is a selective impairment for living things secondary to a disproportionate loss of perceptual knowledge? We found an overall advantage for artifacts even when controlling for several confounding factors. We did not find any relation between direction of category specificity and severity of the disease or between category specificity and loss of knowledge about perceptual or functional attributes.

The present study was aimed at evaluating implicit memory processes in subjects with Williams syndrome (WS) and comparing them to mental-age (MA) matched normal children. For this purpose, tests of verbal and visuo-perceptual explicit memory, verbal and visual repetition priming as well as procedural learning tasks were administered to 12 WS and 12 MA matched subjects. WS subjects showed a level of repetition priming similar to that of MA normal controls. In contrast, WS children showed a reduced learning rate in the two procedural tasks. Although deficient explicit memory and executive dysfunction cannot be excluded from the performance of WS subjects, these results suggest a specific deficit of procedural learning in this particular group of mentally retarded children. This finding is relevant for our knowledge about the qualitative aspects of the anomalous cognitive development in mentally retarded people and the neurobiological substrate underlying this development.

This study aimed at investigating implicit and explicit long-term memory functioning in subjects with Down syndrome (DS) compared to Mental-Age (MA) matched normal children. For this purpose, tests of verbal and visuo-perceptual explicit memory, verbal and visual repetition priming and procedural learning tasks were administered to 14 DS and 20 MA subjects. Our results document comparable implicit memory abilities in the two groups. In contrast, regarding explicit memory, normal children performed better than DS individuals. These results reveal a functional dissociation between implicit and explicit memory in subjects with DS. Theoretical and rehabilitative implications are discussed.

This study evaluated the hypothesis of dissociation between normal lexical but deficient conceptual repetition priming in patients with Alzheimer's disease (AD). For this purpose, we administered to patients with AD and age-matched normal controls the Stem Completion task. In Experiment 1, the level of word processing during study was manipulated by requiring subjects to count vowels (graphemic condition) or generate meanings (semantic condition) of target words. In Experiment 2, the presentation modality was varied during the study to obtain an intramodal and crossmodal repetition priming. Probably due to a floor effect of performance in the graphemic condition, in Experiment 1, AD patients exhibited lower priming than normal controls for the semantically processed words but comparable priming for the graphemically processed ones. In contrast, in Experiment 2, AD patients were poorly primed both in the intra- and crossmodal conditions. Results question the hypothesis of a lexical/conceptual dissociation in the repetition priming exhibited by AD patients and call for other explicative hypotheses of the dissociation between normal and deficient forms of repetition priming in degenerative dementia.

This study aimed at investigating long-term memory functioning in Down's syndrome subjects (DS) as compared to individuals with mental retardation of different etiology (MR) and mental-age matched normal children (MA). For this purpose, tests of verbal and visuo-perceptual explicit memory and a verbal repetition priming task were administered to 15 DS, 15 MR and 30 MA subjects. Our results document comparable verbal priming in the three groups. As for explicit memory, normal children performed better than MR individuals, and these, in turn, better than DS subjects. Compared to MR subjects, DS subjects were particularly deficient in organizing verbal material according to its categorical structure and in actively retrieving stored information. These results support a view positing heterogeneity of neuropsychological deficits across distinct etiology MR groups.

This study was aimed at investigating functional and neuropsychological dissociations between repetition priming and explicit memory tasks. The explicit and implicit versions of the stem completion task were administered to a group of amnesics and a group of control subjects. In Experiment 1 both the explicit and implicit stem completions were significantly higher when the same presentation modality was used for studying and testing than when a change in modality from studying to testing occurred. Amnesics had normal implicit and deficient explicit completion performance. Experiment 2 revealed an advantage of the semantic over the phonological condition only in the explicit task and only in control subjects. Amnesic patients completed the same percentage of words as normal subjects in the phonological and semantic conditions of the implicit task and in the phonological condition of the explicit task but were deficient in intentionally completing semantically processed words. Possible interpretations of these results are discussed according to theoretical models that distinguish memory tasks along an explicit-implicit dichotomy (multiple memory system theory) or along a perceptual-conceptual dichotomy (transfer-appropriate procedures approach), and alternative theoretical positions are evaluated regarding repetition priming and memory deficits in amnesic patients.

This study was devised to investigate immediate and delayed recency effects in anterograde amnesic patients. For this purpose, a word-list immediate recall paradigm and a modified version of the procedure devised by Baddeley and Hitch [Attention and Performance, Erlbaum, NJ, 1977] for eliciting the recency effect in delayed recall conditions was administered to a sample of amnesic patients and to a group of age-matched healthy subjects. Amnesics disclosed a fully normal recency effect in the immediate recall paradigm and a deficient recency effect in the delayed recall condition. These data, taken together with experimental evidence from a patient affected by a pure form of phonological short-term memory impairment [35], draw a double neuropsychological dissociation suggesting a differential origin for the two kinds of recency effects: a short-term memory output underlying enhanced recall of terminal items in immediate recall paradigms, and an ordinal retrieval strategy applied to long-term memory stored units at the root of the delayed recency effect.

In this study we tested the hypothesis that visual repetition priming for words depends upon the accessibility of lexical units in the visual input lexicon. For this purpose, we investigated a dyslexic patient, A.M., whose neuropsychological performances suggested an impaired access to the lexical route of reading. According to the predictions, Experiments 1 and 2 demonstrated deficient priming in tests involving the visual presentation of words (Word Identification and Stem Completion). In Experiment 3, we demonstrated that A.M.'s deficient priming was specific for visually presented words, in that the auditory presentation elicited a normal priming effect (auditory Stem Completion). These data are discussed in the light of a theoretical framework suggesting a fractionation of the modalities by which repetition priming can be elicited, each mediated by a particular memory subsystem.

This study investigated the contribution of perceptual and conceptual processes to the repetition priming effect, and evaluated alternative theoretical positions about repetition priming in amnesic patients. Toward this end, we administered three repetition priming tasks (Stem Completion, Word Identification and Free Association) and an explicit memory task (yes/no Recognition) to amnesic and alcoholic patients, and tested the sensitivity of these tasks to level of processing and to manipulations of presentation modality. Experiment 1 demonstrated that the level of priming in Stem Completion and Free Association (but not in Word Identification) was enhanced by semantic elaboration of the stimuli. Experiment 2 revealed that the magnitude of priming in Word Identification and Stem Completion (but not in Free Association) was larger in the intramodal then in the intermodal condition. Amnesic patients displayed normal perceptual as well conceptual priming. Possible interpretations of these results according to theoretical models that distinguish memory tasks along an explicit-implicit dichotomy (multiple memory system theory), or on the basis of the extent to which they depend upon perceptual or conceptual processing (transfer-appropriate procedures approach), or that assumes a possible contamination of priming performance by explicit strategies of retrieval are discussed.

The early position that prosopagnosia is predominantly associated with right hemisphere (RH) injury was challenged by the finding that in practically all cases that come to autopsy pathological data point to bilateral damage. Yet the rejection of the RH hypothesis may have been too hasty. We report three prosopagnosic patients in whom MRI and CT documented a lesion confined to the right occipito-temporal areas and PET confirmed that hypometabolism involved the RH only. A review of the literature brought out 27 cases with neuroimaging evidence that prosopagnosia was associated with RH damage plus four cases with surgical evidence. It remains, however, that the inability to recognize familiar faces is a rare disorder, not manifested by the majority of patients with right temporo-occipital injury. We submit that right-handers differ in the degree of their RH specialization in processing faces and that in only a minority of them is it so marked that it cannot be compensated for by the healthy left hemisphere.