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It has been proposed that the maintenance of phonological information in verbal working memory (vWM) is carried by a domain-specific short-term storage center-the phonological loop-which is composed of a phonological store and an articulatory rehearsal system. Several brain regions including the left posterior inferior frontal gyrus (pIFG) and anterior supramarginal gyri (aSMG) are thought to support these processes. However, recent behavioral evidence suggests that verbal and non-verbal auditory information may be processed as part of a unique domain general short-term storage center instead of through specialized subsystems such as the phonological loop. In the current study, we used a single-pulse transcranial magnetic stimulation (TMS)-delayed priming paradigm with speech (syllables) and acoustically complex non-speech sounds (bird songs) to examine whether the pIFG and aSMG are involved in the processing of verbal information or, alternatively, in the processing of any complex auditory information. Our results demonstrate that TMS delivered to both regions had an effect on performance for speech and non-speech stimuli, but the nature of the effect was different. That is, priming was reduced for the speech sounds because TMS facilitated the detection of different but not identical stimuli, and accuracy was decreased for non-speech sounds. Since TMS interfered with both speech and non-speech sounds, these findings support the existence of an auditory short-term storage center located within the dorsal auditory stream.

Judgments of spatial relationships are often made when the object or observer is moving. Behaviourally, there is evidence that these 'dynamic' judgments of spatial extent differ from static judgments. For example, in one of the simplest probes of spatial extent--the line bisection task--the typically observed leftward bisection bias of about 1% of line length is increased considerably after left-to-right scanning. Here we used fMRI to examine whether or not different brain regions would be involved in static and dynamic judgments of spatial extent. Dynamic (i.e., scan the line prior to bisecting) relative to static ocular bisections (i.e., line bisection by fixation) produced activations in the cuneus and precuneus bilaterally, with reduced activation relative to static judgments observed in the supramarginal gyrus bilaterally. Dynamic bisections relative to a control condition (i.e., scan a line and then saccade to a transection mark) produced activations in the precuneus/superior parietal lobe bilaterally and left cerebellum. Only marginal evidence was found for different activations due to the initial scan direction of the line. These results highlight the fact that dynamic judgments of spatial extent use distinct brain regions from those employed to make static judgments, and the same mechanism is employed independent of scan direction. It may be the case that velocity processing and time estimates are integrated primarily in the cuneus and precuneus to produce estimates of spatial extent under dynamic scanning conditions.

Although it is known that sounds can affect visual perception, the neural correlates for crossmodal interactions are still disputed. Previous tracer studies in non-human primates revealed direct anatomical connections between auditory and visual brain areas. We examined the structural connectivity of the auditory cortex in normal humans by diffusion-weighted tensor magnetic resonance imaging and probabilistic tractography. Tracts were seeded in Heschl's region or the planum temporale. Fibres crossed hemispheres at the posterior corpus callosum. Ipsilateral fibres seeded in Heschl's region projected to the superior temporal sulcus, the supramarginal gyrus and intraparietal sulcus and the occipital cortex including the calcarine sulcus. Fibres seeded in the planum temporale terminated primarily in the superior temporal sulcus, the supramarginal gyrus, the central sulcus and adjacent regions. Our findings suggest the existence of direct white matter connections between auditory and visual cortex--in addition to subcortical, temporal and parietal connections.

Experimental behavioral data show that written action descriptions are remembered better when encoded by enacting them compared with merely verbal encoding. To explore this facilitating effect of encoding by performing actions ('enactment effect'), a functional magnetic resonance imaging (fMRI) study was conducted with n=18 normal subjects. During a learning condition, subjects encoded action phrases like 'cut the bread' either by reading aloud or by enacting them. The same phrases plus additional distractors were presented during fMRI scanning, and the task was to decide (yes/no key press) whether a displayed phrase was previously learned or whether it was a new one. Retrieval - independent of encoding type - activated anterior cingulate, SMA, and visual cortex bilaterally. Activations of the inferior frontal and sensorimotor cortex, and the precentral sulcus, were only left sided. The right cerebellum was also activated. The subtraction of the brain activations in the verbal condition from the enactment condition resulted in significant clusters located in middle temporal and inferior parietal left cortical areas, and, on the right side, in superior temporal, postcentral and inferior parietal cortical areas. Most striking were the bilateral inferior parietal activations, covering the supramarginal gyrus (SMG). Therefore it is concluded that SMG may be a central structure in a neurofunctional explanation of the enactment effect.

Chinese is a logographic language system that differs from alphabetic languages, and some of the neurocognitive mechanisms underlying Chinese logographic reading also differ from those underlying alphabetic word reading. However, whether education level effects the neural activation associated with logographic processing of Chinese is still unknown. In the present study, 11 Chinese illiterate and 11 literate (age-matched) subjects participated in an event-related fMRI experiment with Chinese character discrimination (CD) and figure discrimination (FD) tasks. All subjects were asked to view the character or figure pairs and discriminate whether the characters or figures of each stimuli pair were the same or not using response keys. Both literate and illiterate subjects activated a widely distributed cerebral network, including the bilateral inferior, middle and superior frontal gyri, superior temporal gyrus and parietal lobe, in the CD task. Finally, we directly compared the activations of literate subjects with illiterate subjects. The results suggest that the bilateral parts of the angular gyrus and supramarginal gyrus are more active for literate than illiterate subjects in the CD task. We found no significant group difference in the FD task. Therefore, the present results may indicate that education level effects the neural activation associated with the logographic processing of Chinese.

Previous neuroimaging studies yielded different patterns of brain areas activated during sensorimotor adaptation, when sensory conflicts are introduced, e.g. by manipulating visual information. We propose that possible reasons might be the lack to control for adaptation or the change in motor performance. In consequence, it was not possible to distinguish between adaptation-related and error-related brain activations. We have developed a sensorimotor adaptation task which controls for these errors using two types of visual distortion and thus is suited to disambiguate sensorimotor adaptation from the related activation patterns. Twenty healthy subjects were scanned by fMRI during a tracking task, while adapting to a visual distortion, which depended either on hand position or on hand velocity. In either case, adaptation was interleaved with a control condition, designed such that the time-course of tracking errors approximated that under visual distortion. We found that adaptation-related neural activation was limited to the left supramarginal and angular gyrus under the position-dependent distortion, but extended bilaterally in the supramarginal gyrus, as well as in the left middle and right superior frontal gyrus under the velocity-dependent distortion. Our findings confirm that equating the errors under both conditions will yield an anatomically more restricted activation pattern compared with other studies. The additional recruitment in right parietal and bilateral frontal areas under the velocity-dependent distortion might reflect a higher computational demand, or the involvement of different adaptive mechanisms.

We used positron emission tomography (PET) to measure movement set-related changes in regional cerebral blood flow (rCBF) when human subjects were asked to copy hand movements. Movement set-related activity in the brain is thought to reflect the processes of movement selection, preparation and inhibition. Four conditions were used. In the first condition, prepare and execute (PE), the hand stimulus to be copied was shown to subjects 3 s before an auditory "go"-cue instructed subjects to execute the movement; a large part of the scanning time was therefore spent in preparing to move. In the immediate execution condition (E), the hand stimulus and the go cue were presented simultaneously. The prepare-only condition (P) was similar to PE, except subjects only prepared to make the movement and did not actually execute any movement when they heard the auditory go-cue. The same stimuli were presented in a baseline condition (B), but the subjects were instructed to neither prepare nor execute movements. There were 5 principle findings: (1) In contrast to a previous study of human set-related activity in which movements were instructed by an arbitrary pattern of LEDs, preparing to make a copied movement causes rCBF changes in area 44 in posterior Broca's area; (2) set-related activity can be recorded in the cerebellar hemispheres and midline; (3) we confirmed that the supramarginal gyrus has a general role in preparing movements - there was more rCBF in the P than the E condition; (4) the cerebellar nuclei and the basal ganglia may be particularly involved in the initiation and execution of a planned movement; these regions were more active in the PE condition than the P condition; (5) the ventrolateral prefrontal cortex and a left anterior cingulate area are part of a distributed system involved in the suppression of a motor response; these areas were significantly more active in the P than the PE condition.

We examined the somatosensory perceptions evoked by stimulation of rolandic and parietal brain regions in 40 epileptic patients undergoing a presurgical investigation with intracerebral electrodes. Bipolar stimulation trains were delivered in an incremental sequence at medial and/or lateral contact pairs of stereotaxically implanted, multi-contact electrodes, while monitoring stimulus after discharge propagation with electrodes in frontal and temporal lobes. Rolandic stimulation evoked contralateral sensations, whereas sensations from either side were evoked in the opercular region. Stimulation of lateral posterior parietal cortex evoked only few sensations and these were restricted to the supramarginal gyrus. Contralateral sensations were evoked in the posterior cingulate gyrus, whereas ipsilateral sensations were evoked in the vicinity of the cingulate sulcus. Complex proprioceptive sensations in the form of bilateral feelings of levitation were elicited in a medial parietal region around the subparietal sulcus and not at any other site. These perceptions were not accompanied by any movement, tactile, or vestibular sensations, suggesting that the human sub-parietal sulcus region is linked to the proprioceptive processing system.