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Cognitive reserve (CR) is the brain's capacity to cope with cerebral damage to minimize clinical manifestations. The 'passive model' considers head or brain measures as anatomical substrates of CR, whereas the 'active model' emphasizes the use of brain networks effectively. Sixteen healthy subjects, 12 amnestic mild cognitive impairment (MCI) and 16 cases with mild Alzheimer's disease (AD) were included to investigate the relationships between proxies of CR and cerebral measures considered in the 'passive' and 'active' models. CR proxies were inferred premorbid IQ (WAIS Vocabulary test), 'education-occupation', a questionnaire of intellectual and social activities and a composite CR measure. MRI-derived whole-brain volumes and brain activity by functional MRI during a visual encoding task were obtained. Among healthy elders, higher CR was related to larger brains and reduced activity during cognitive processing, suggesting more effective use of cerebral networks. In contrast, higher CR was associated with reduced brain volumes in MCI and AD and increased brain function in the latter, indicating more advanced neuropathology but that active compensatory mechanisms are still at work in higher CR patients. The right superior temporal gyrus (BA 22) and the left superior parietal lobe (BA 7) showed greatest significant differences in direction of slope with CR and activation between controls and AD cases. Finally, a regression analysis revealed that fMRI patterns were more closely related to CR proxies than brain volumes. Overall, inverse relationships for healthy and pathological aging groups emerged between brain structure and function and CR variables.

Background Harlow's report of the case of Phineas P. Gage in 1848 was one of the earliest description of the personality and behavioral changes following frontal lobe damage. Since Harlow's articles, a few more case reports of frontal lobe damage have been published. As standard neuropsychological and neurologic evaluations may reveal subtle defects, case reports have been particularly useful in characterizing the behavioral changes that follow frontal lobe damage. Objective To describe the long-term outcome of an 81-year-old patient who sustained a severe frontal brain lesion 60 years ago caused by the passage of an iron spike through his head. Results The patient has bilateral damage affecting the orbital and dorsolateral frontal regions. He displays many of the typical frontal behavioral disturbances described in the literature. His conduct is characterized by dependence on others, cheerfulness, planning difficulties, problems establishing realistic goals, lack of drive, and difficulties in initiating, continuing, and finishing activities. Although gross cognitive functioning is intact, neuropsychological deficits are present in the executive functioning, memory, and visuoconstructive domains. Conclusions In contrast with the antisocial conduct pattern usually associated with frontal damage in the literature, this case suggests that large frontal lesions can produce behavioral and personality changes that are compatible with stable functioning in family, professional, and social settings. In addition to the localization of the lesion, many other factors should be considered in the long-term prognosis of frontal brain injured patients.

The Stroop is a classical paradigm that presumably involves the inhibition of automatic responses and is frequently used to assess the frontal lobe functions. We investigated the effect of discrete prefrontal lesions in a Stroop task. A sample of 32 patients with frontal lesions were matched with normal controls by sex, age and years of education. Significant differences between patients and controls were found for errors but not for reaction time. Regression analysis showed that the region most related to errors was the right prefrontal lateral cortex. Left lobectomies did not impair the Stroop performance. Our results favour the role of the right prefrontal cortex in sustained attention, and disagree with the conception of the left prefrontal cortex having a role in the inhibition of verbal automatic responses.

Neuroanatomical correlates of the estimation of occurrence frequency have received little attention. This study investigates the possible role of the frontal lobe in estimating word occurrence frequency. A sample of 27 patients with frontal lesions were matched with normal controls by sex, age and years of education. Significant differences between patients and controls were found for frequency estimation, but not for item recognition. Studying accuracy of estimation as a function of actual frequency, the frontal group performed worse, especially at high frequencies of occurrence. As far as lesion lateralization is concerned, the right frontal subgroup performed worse than the control group in the estimation of frequency. Our results suggest that the prefrontal cortex plays a role in estimating word occurrence and that there is a dissociation between frequency memory and recognition memory, pointing to the involvement of two different cerebral systems.

The purpose of this study was to investigate the effect of focal frontal lesions, identified by magnetic resonance imaging (MRI), in a group of traumatic brain injured (TBI) patients, in order to clarify the sensitivity of phonemic and semantic fluency tasks as tests of frontal lobe functioning. Thirteen TBI patients were included and matched with a normal control group of 26 subjects. Frontal lobe patients produced significantly fewer words than the control group in the phonemic fluency condition. Semantic performance correlated with lesion size, but phonemic performance did not, corroborating the idea that the two have different brain-based substrates. Although, as a group effect, frontal lesions impaired fluency, not all patients were impaired, even in the presence of large bilateral frontal lesions.