Differential activation in parahippocampal and prefrontal cortex during word and face encoding tasks

Episodic encoding is the first step in the formation of a memory trace. The relation between type of stimulus material and regional brain activation is not fully understood. We measured brain activation using fMRI in 12 healthy subjects during two experiments, word and face encoding. A widespread network of common activations in both tasks was present in the bilateral frontal (BA44/45), occipital (BA17/18/19) and fusiform gyri (BA37) as well as the right hippocampal formation (BA30). A region-of-interest-analysis for the hippocampal formation and dorsolateral prefrontal cortex (DLPFC) was performed additionally. During face encoding the right dorsal and during word encoding the bilateral ventral hippocampal region was activated. In the prefrontal cortex a lateralization to the left side was present only for word encoding. During encoding, activation in the inferior frontal and hippocampal cortex is modulated by the type of stimulus material.     

Evidence for asymmetric frontal-lobe involvement in episodic memory from functional magnetic resonance imaging and patients with unilateral frontal-lobe excisions

Recently, there has been considerable debate regarding the involvement of the left and right prefrontal cortices in the encoding and retrieval of episodic memory. In a previous PET study, we found that the use of easily verbalisable material may lead to activation predominantly in the left lateral frontal cortex whilst the use of non-easily verbalisable material may lead to activation predominantly in the right lateral frontal cortex, in both cases irrespective of encoding and retrieval processes. In order to replicate and extend these findings, the same task was modified for use with fMRI. Six healthy volunteers were scanned while encoding and then recalling stimuli that either emphasised visual or verbal processes. It was found that, in comparison to a baseline condition, the encoding of visual stimuli led to a bilateral activation of the prefrontal cortex whilst the encoding of verbal stimuli led to a preferential activation of the left prefrontal cortex. An effect of stimulus type was less evident during retrieval, with both visual and verbal stimuli leading to bilateral prefrontal cortex activation. Overall, encoding and retrieval activated similar regions of the prefrontal cortex suggesting that these areas mediate processes that are fundamental to both aspects of memory. To extend these findings further, the tasks used in the fMRI study were used to assess a group of patients with unilateral frontal lesions and a group of healthy control volunteers. The patients were significantly impaired compared to the healthy volunteers, although no significant differences were found in performance between the right- and left-sided lesioned patients. This result suggests that the memory-related asymmetries observed during functional neuroimaging studies may not be critical for task performance.     

Abnormal parietal cortex activation during working memory in schizophrenia: verbal phonological coding disturbances versus domain-general executive dysfunction

OBJECTIVE: The goal of this study was to determine whether the regions of the prefrontal and parietal cortices showing abnormal activation among individuals with schizophrenia during working memory tasks are associated with either 1) phonological coding processes that may be specific to verbal tasks (i.e., ventral prefrontal and parietal cortices) or 2) domain-general executive processes engaged by verbal and nonverbal tasks (i.e., dorsal prefrontal and parietal cortices). METHOD: The participants were 57 medicated individuals with schizophrenia and 120 healthy subjects. Functional magnetic resonance imaging was used to scan all participants during performance of verbal and nonverbal 2-back working memory tasks. RESULTS: In the healthy subjects there was similar bilateral dorsal prefrontal and inferior parietal cortex activation for both the verbal and nonverbal working memory tasks, but greater left ventral prefrontal and parietal cortex activation during verbal compared to nonverbal working memory. Individuals with schizophrenia showed bilateral deficits in dorsal frontal and parietal activation during both verbal and nonverbal working memory tasks. They also demonstrated the typical pattern of greater activity for verbal, as compared to nonverbal, working memory in ventral prefrontal and parietal regions, although they showed less verbal superiority in a left ventral prefrontal region. CONCLUSIONS: These results support the hypothesis that working memory deficits in individuals with schizophrenia reflect deficits in activation of brain regions associated with the central executive components of working memory rather than domain-specific storage buffers.     

The effect of encoding strategy on the neural correlates of memory for faces

Encoding and recognition of unfamiliar faces in young adults were examined using positron emission tomography to determine whether different encoding strategies would lead to encoding/retrieval differences in brain activity. Three types of encoding were compared: a 'deep' task (judging pleasantness/unpleasantness), a 'shallow' task (judging right/left orientation), and an intentional learning task in which subjects were instructed to learn the faces for a subsequent memory test but were not provided with a specific strategy. Memory for all faces was tested with an old/new recognition test. A modest behavioral effect was obtained, with deeply-encoded faces being recognized more accurately than shallowly-encoded or intentionally-learned faces. Regardless of encoding strategy, encoding activated a primarily ventral system including bilateral temporal and fusiform regions and left prefrontal cortices, whereas recognition activated a primarily dorsal set of regions including right prefrontal and parietal areas. Within encoding, the type of strategy produced different brain activity patterns, with deep encoding being characterized by left amygdala and left anterior cingulate activation. There was no effect of encoding strategy on brain activity during the recognition conditions. Posterior fusiform gyrus activation was related to better recognition accuracy in those conditions encouraging perceptual strategies, whereas activity in left frontal and temporal areas correlated with better performance during the 'deep' condition. Results highlight three important aspects of face memory: (1) the effect of encoding strategy was seen only at encoding and not at recognition; (2) left inferior prefrontal cortex was engaged during encoding of faces regardless of strategy; and (3) differential activity in fusiform gyrus was found, suggesting that activity in this area is not only a result of automatic face processing but is modulated by controlled processes.     

Event-related fMRI of frontotemporal activity during word encoding and recognition in schizophrenia

OBJECTIVE: Neuropsychological studies have demonstrated verbal episodic memory deficits in schizophrenia during word encoding and retrieval. This study examined neural substrates of memory in an analysis that controlled for successful retrieval. METHOD: Event-related blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to measure brain activation during word encoding and recognition in 14 patients with schizophrenia and 15 healthy comparison subjects. An unbiased multiple linear regression procedure was used to model the BOLD response, and task effects were detected by contrasting the signal before and after stimulus onset. RESULTS: Patients attended during encoding and had unimpaired reaction times and normal response biases during recognition, but they had lower recognition discriminability scores, compared with the healthy subjects. Analysis of contrasts was restricted to correct items. Previous findings of a deficit in bilateral prefrontal cortex activation during encoding in patients were reproduced, but patients showed greater parahippocampal activation rather than deficits in temporal lobe activation. During recognition, left dorsolateral prefrontal cortex activation was lower in the patients and right anterior prefrontal cortex activation was preserved, as in the authors' previous study using positron emission tomography. Successful retrieval was associated with greater right dorsolateral prefrontal cortex activation in the comparison subjects, whereas orbitofrontal, superior frontal, mesial temporal, middle temporal, and inferior parietal regions were more active in the patients during successful retrieval. CONCLUSIONS: The pattern of prefrontal cortex underactivation and parahippocampal overactivation in the patients suggests that functional connectivity of dorsolateral prefrontal and temporal-limbic structures is disrupted by schizophrenia. This disruption may be reflected in the memory strategies of patients with schizophrenia, which include reliance on rote rehearsal rather than associative semantic processing.     

Retrieval success is accompanied by enhanced activation in anterior prefrontal cortex during recognition memory: an event-related fMRI study

Neural regions associated with retrieval success were identified using event-related fMRI procedures and randomly ordered trials on a recognition memory test. Differences between hits and correct rejections (CRs) occurred multiple regions, including bilateral anterior and right dorsolateral prefrontal cortex, bilateral inferior parietal cortex, and right superior parietal cortex (all hits > CRs), and right occipital cortex (CRs > hits). The hit > CR pattern is not compromised by time-on-task explanations because response latencies for correctly rejected words exceeded those for hits. Converging evidence for the claim that the hit > CR pattern identified neural correlates of retrieval success was obtained by unconfounding item history and retrieval success. That is, we implemented a third condition in which nonstudied words were presented, yet retrieval success was hypothesized to facilitate CRs of these lures. Specifically, in when confronted with a familiar, yet nonstudied word, (e.g., nosedive after studying nosebleed and skydive), subjects might adopt a strategy whereby they recall the studied word(s) that gave rise to the familiarity (nosebleed, skydive) and thereby reject the lure. This method of instantiating retrieval success under conditions in which the target word had not been studied offers converging evidence for the claim that anterior-prefrontal cortex (among other regions) demonstrates enhanced activation during retrieval success.     

Differences of cerebral activation between superior and inferior learners during motor sequence encoding and retrieval

Cerebral activation during memory encoding and retrieval might depend on subjects' learning capacity, either by corresponding to better performance in superior learners or by reflecting increased effort in inferior learners. To investigate these alternative hypotheses, the study compared cerebral activation during encoding and retrieval of a motor sequence in groups of subjects with superior and inferior learning performances. Ten healthy subjects underwent functional magnetic resonance imaging (fMRI) while performing a motor sequence encoding paradigm (i.e. finger tapping sequence) and a retrieval paradigm (i.e. reproduction of the learned sequence). Subjects were divided into superior and inferior learners according to the correctness of sequence reproduction during retrieval. During encoding, there was strong bilateral activation in the middle frontal gyrus, the supplementary motor area (SMA), the lateral parietal lobe and the cerebellum. During retrieval, again strong activation was found in identical areas of the prefrontal cortex, the parietal lobe and the cerebellum. During encoding, inferior learners showed more left-sided activations in the left middle frontal and inferior parietal gyri. Superior learners showed increased activation in the corresponding right-sided brain areas during encoding as well as during retrieval. Differences of cerebral activations in the prefrontal and parietal cortex during encoding and retrieval were found to be related to retrieval performance, i.e. success and effort. Further intervention studies are needed to assess whether these interindividual differences are the cause or the consequence of differences in memory performance.     

An FMRI study of episodic encoding and recognition of words in patients with schizophrenia in remission

OBJECTIVE: Verbal memory deficits are among the most severe cognitive deficits observed in patients with schizophrenia. This study examined patterns of brain activity during episodic encoding and recognition of words in patients with schizophrenia. METHOD: Functional magnetic resonance imaging (fMRI) was used to study regional brain activation in 10 healthy male comparison subjects and 10 male outpatients with schizophrenia during performance of a modified version of the words subtest of Warrington's Recognition Memory Test. RESULTS: Despite having intact performance in word recognition, the patients with schizophrenia had less activation of the right dorsolateral and anterior prefrontal cortex, right anterior cingulate, and left lateral temporal cortex during word encoding, compared with the healthy comparison subjects. During word recognition, the patients had impairments in activation of the bilateral dorsolateral prefrontal and lateral temporal cortices. CONCLUSIONS: Schizophrenia was associated with attenuated frontotemporal activation during episodic encoding and recognition of words. These results from an fMRI study replicate earlier findings derived from a positron emission tomography study.     

Anterior hippocampus orchestrates successful encoding and retrieval of non-relational memory: an event-related fMRI study

Episodic memory encoding and retrieval processes have been linked to different neural networks. However, the common brain regions associated with non-relational memory processing during successful encoding (subsequent memory effect) and successful retrieval (recognition effect) have not yet been investigated. Further, the majority of functional imaging studies have been conducted in young subjects, whereas patients from lesion studies, where most neuropsychological models are still based upon, are usually older. Inferences from younger subjects cannot necessarily be applied to the elderly, an issue becoming particularly relevant with our ageing society. Using an event-related fMRI approach we studied 29 healthy elderly subjects (mean age 67.8, SD 5.4 years) with a non-associative task of intentional word list encoding and retrieval. For each subject, behavioural responses were individually classified into four event types (hits test, misses test, false alarms, correct rejections). Brain areas activated during successful memory encoding comprised the anterior left hippocampus extending into the surrounding parahippocampal gyrus. Regions associated with successful memory retrieval involved a wide-spread network of anterior left parahippocampal gyrus, bilateral temporal cortices and bilateral ventral and dorsal prefrontal areas. Regions contributing to both successful encoding and retrieval, evidenced by a conjunction analysis, revealed prominent left lateralized activations of the anterior hippocampus and the inferior parietal lobe. Our results indicate that the anterior left hippocampus plays an important role during successful memory encoding and during successful memory retrieval in a task of simple, non-associative wordlist learning in healthy elderly subjects.     

Neural correlates of memory for items and for associations: an event-related functional magnetic resonance imaging study

Although results from cognitive psychology, neuropsychology, and behavioral neuroscience clearly suggest that item and associative information in memory rely on partly different brain regions, little is known concerning the differences and similarities that exist between these two types of information as a function of memory stage (i.e., encoding and retrieval). We used event-related functional magnetic resonance imaging to assess neural correlates of item and associative encoding and retrieval of simple images in 18 healthy subjects. During encoding, subjects memorized items and pairs. During retrieval, subjects made item recognition judgments (old vs. new) and associative recognition judgments (intact vs. rearranged). Relative to baseline, item and associative trials activated bilateral medial temporal and prefrontal regions during both encoding and retrieval. Direct contrasts were then performed between item and associative trials for each memory stage. During en- coding, greater prefrontal, hippocampal, and parietal activation was observed for associations, but no significant activation was observed for items at the selected threshold. During recognition, greater activation was observed for associative trials in the left dorsolateral prefrontal cortex and superior parietal lobules bilaterally, whereas item recognition trials showed greater activation of bilateral frontal regions, bilateral anterior medial temporal areas, and the right temporo-parietal junction. Post hoc analyses suggested that the anterior medial temporal activation observed during item recognition was driven mainly by new items, confirming a role for this structure in novelty detection. These results suggest that although some structures such as the medial temporal and prefrontal cortex play a general role in memory, the pattern of activation in these regions can be modulated by the type of information (items or associations) interacting with memory stages.     

Imaging cognition II: An empirical review of 275 PET and fMRI studies

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/motion), language (written/spoken word recognition, spoken/no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration.     

Alterations in amplitude of low frequency fluctuation in treatment‐naïve major depressive disorder measured with resting‐state fMRI

There are limited resting‐state functional magnetic resonance imaging (fMRI) studies in major depressive disorder (MDD). Of these studies, functional connectivity analyses are mostly used. However, a new method based on the magnitude of low frequency fluctuation (LFF) during resting‐state fMRI may provide important insight into MDD. In this study, we examined the amplitude of LFF (ALFF) within the whole brain during resting‐state fMRI in 30 treatment‐naïve MDD subjects and 30 healthy control (HC) subjects. When compared with HC, MDD subjects showed increased ALFF in the frontal cortex (including the bilateral ventral/dorsal anterior cingulate cortex, orbitofrontal cortex, premotor cortex, ventral prefrontal cortex, left dorsal lateral frontal cortex, left superior frontal cortex), basal ganglia (including the right putamen and left caudate nucleus), left insular cortex, right anterior entorhinal cortex and left inferior parietal cortex, together with decreased ALFF in the bilateral occipital cortex, cerebellum hemisphere, and right superior temporal cortex. These findings may relate to characteristics of MDD, such as excessive self‐referential processing and deficits in cognitive control of emotional processing, which may contribute to the persistent and recurrent nature of the disorder. Hum Brain Mapp 35:4979–4988, 2014. © 2014 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.     

Engagement of lateral and medial prefrontal areas in the ecphory of sad and happy autobiographical memories

Autobiographic memory is usually affect-laden, either positively or negatively. A central question is whether the retrieval of both emotive forms of memory engages the same or a different neural net. To test this we studied 13 normal subjects with functional magnetic resonance imaging while they retrieved a number of distinct episodes, all of which were either rated as strongly positive (happy) or strongly negative (sad) in affect. Comparing the retrieval of sad with that of happy episodes revealed activation in both lateral orbital cortices symmetrically (extending into the ventrolateral prefrontal cortex as well), together with a small region in the right lateral temporal cortex and the left cerebellum. Vice versa, comparing the retrieval of happy with that of sad episodes revealed a major activation in the left hippocampal region, bilateral (though more right-sided) activation in the medial orbitofrontal/subgenual cingulate and a left sided activation in the dorsolateral prefrontal activation. These findings point to the importance of the orbitofrontal cortex for affect- laden information processing and to the existence of distinct neural nets for the re-activation of positively and negatively viewed autobiographic episodes.     

Brain regions associated with episodic retrieval in normal aging and Alzheimer's disease.

OBJECTIVE: To examine patterns of brain activation during verbal episodic retrieval in normal elderly subjects and patients in an early phase of AD. BACKGROUND: It is established that 1) a profound episodic memory impairment is a cardinal symptom of AD; and 2) some of the earliest brain changes in this disease occur in regions critical to episodic memory, such as the hippocampus and neighboring regions. Yet, it remains largely unknown whether the episodic memory deficit seen in AD is paralleled by concomitant alterations in brain activity during actual task performance in these or other brain areas. METHODS: Using PET, blood flow was assessed in normal elderly subjects and patients with early AD during two retrieval conditions involving completion of word stems: baseline and cued recall. RESULTS: The patients with AD showed a marked performance deficit in cued recall, although the two groups were indistinguishable in the baseline task condition. Both groups showed bilateral activity in orbital and dorsolateral prefrontal cortex, left precuneus, and right cerebellum, as well as decreased activity in distinct left temporal regions during cued recall. The normal elderly alone activated the left parietal cortex and the left hippocampal formation during episodic retrieval. By contrast, AD-related increases in activity during cued recall were observed in the left orbital prefrontal cortex and left cerebellum. CONCLUSIONS: The similar patterns of activations in the two groups suggest that a large distributed network involved in episodic memory retrieval functions relatively normally in early AD. Those retrieval activations seen in the normal elderly, as opposed to the patients, may reflect AD-related failures in semantic processing and successful recollection of the target information, respectively. Finally, the AD-related increases in activity were interpreted in terms of compensatory reactions to the difficulties in performing the episodic memory task.     

An fMRI study of the functional neuroanatomy of picture encoding in younger and older adults

Age-related changes in the neural mechanisms of picture encoding were investigated using functional magnetic resonance imaging (fMRI). Seven younger and seven older adults were studied while they were encoding pairs of concrete-related, concrete-unrelated, and abstract pictures. Functional (T2*-weighted) and anatomical (T1-weighted) images of the brain were obtained using a 1.5 T MRI scanner. The results in the younger adults showed that the left dorsal prefrontal cortex (PFC) was activated during associative learning of the concrete-unrelated or abstract pictures. The results also suggest that both ventral and dorsal visual pathways are involved in the encoding of abstract pictures, and that the right superior parietal lobule likely mediates spatial information of the abstract pictures. The older adults showed significant activation in the left dorsal PFC under concrete-unrelated and abstract conditions. However, the older adults failed to activate either the left ventral and right dorsal PFC under the concrete-unrelated condition, or the parietal areas under abstract condition. A direct comparison between the two age groups demonstrates that the older adults had a reduced activation in the bilateral parieto-temporo-occipital areas under abstract condition, and in the right temporo-occipital area extending to the fusiform gyrus under the concrete-unrelated condition. Finally, age difference was found in correlation between memory performance and amplitude of signal change in the parahippocampal gyrus and fusiform gyrus under the concrete-unrelated and abstract conditions. These changes in neural response likely underlie the age-related memory decline in relation to pictorial information.     

Effect of schizophrenia on frontotemporal activity during word encoding and recognition: a PET cerebral blood flow study.

OBJECTIVE: Neuropsychological studies have shown that deficits in verbal episodic memory in schizophrenia occur primarily during encoding and retrieval stages of information processing. The current study used positron emission tomography to examine the effect of schizophrenia on change in cerebral blood flow (CBF) during these memory stages. METHOD: CBF was measured in 23 healthy comparison subjects and 23 patients with schizophrenia during four conditions: resting baseline, motor baseline, word encoding, and word recognition. The motor baseline was used as a reference that was subtracted from encoding and recognition conditions by using statistical parametric mapping. RESULTS: Patients' performance was similar to that of healthy comparison subjects. During word encoding, patients showed reduced activation of left prefrontal and superior temporal regions. Reduced left prefrontal activation in patients was also seen during word recognition, and additional differences were found in the left anterior cingulate, left mesial temporal lobe, and right thalamus. Although patients' performance was similar to that of healthy comparison subjects, left inferior prefrontal activation was associated with better performance only in the comparison subjects. CONCLUSIONS: Left frontotemporal activation during episodic encoding and retrieval, which is associated with better recognition in healthy people, is disrupted in schizophrenia despite relatively intact recognition performance and right prefrontal function. This may reflect impaired strategic use of semantic information to organize encoding and facilitate retrieval.     

A functional magnetic resonance imaging study of bipolar disorder: state- and trait-related dysfunction in ventral prefrontal cortices

BACKGROUND: Abnormalities in prefrontal and anterior cingulate cortices are implicated in disturbances of attention, cognition, and impulse regulation in bipolar disorder. Acute episodes have been associated with dysfunction in these brain regions, and more enduring trait-related dysfunction has been implicated by volumetric and cellular abnormalities in these regions. The relative contributions of prefrontal regions to state and trait disturbances in bipolar disorder, however, have not been defined. We sought to characterize state- and trait-related functional impairment in frontal systems in bipolar disorder. METHODS: Thirty-six individuals with bipolar disorder I (11 with elevated, 10 with depressed, and 15 with euthymic mood states) and 20 healthy control subjects matched for handedness and sex participated in an event-related functional magnetic resonance imaging study of the color-word Stroop to determine mean percentage of regional task-related signal change. RESULTS: Signal increased during the Stroop task similarly across diagnostic groups in a distribution that included dorsal anterior cingulate and prefrontal cortices, consistent with previously reported activations in this task. Signal changes associated with specific mood states in bipolar disorder were detected in ventral prefrontal cortex, with a blunted increase in signal on the right side in the elevated mood group (P =.005) and an exaggerated increase in signal on the left side in the depressed group (P =.02) compared with the euthymic group. Patients (vs healthy controls) demonstrated blunted activation in a spatially distinct, rostral region of left ventral prefrontal cortex that was independent of mood state (P<.005). CONCLUSIONS: Bipolar disorder is associated with a trait abnormality in left ventral prefrontal cortex. Additional ventral prefrontal abnormalities may be associated with specific acute mood states. The hemispheric laterality of the abnormality and the directions of signal change may relate to the valence of the mood episode.     

Emotional and temporal aspects of situation model processing during text comprehension: an event-related fMRI study

Language comprehension in everyday life requires the continuous integration of prior discourse context and general world knowledge with the current utterance or sentence. In the neurolinguistic literature, these so-called situation model building processes have been ascribed to the prefrontal cortex or to the right hemisphere. In this study, we use whole-head event-related fMRI to directly map the neural correlates of narrative comprehension in context. While being scanned using a spin-echo sequence, 20 participants listened to 32 short stories, half of which contained globally inconsistent information. The inconsistencies concerned either temporal or chronological information or the emotional status of the protagonist. Hearing an inconsistent word elicited activation in the right anterior temporal lobe. The comparison of different information aspects revealed activation in the left precuneus and a bilateral frontoparietal network for chronological information. Emotional information elicited activation in the ventromedial prefrontal cortex and the extended amygdaloid complex. In addition, the integration of inconsistent emotional information engaged the dorsal frontomedial cortex (Brodmann's area 8/9), whereas the integration of inconsistent temporal information required the lateral prefrontal cortex bilaterally. These results indicate that listening to stories can elicit activation reflecting content-specific processes. Furthermore, updating of the situation model is not a unitary process but it also depends on the particular requirements of the text. The right hemisphere contributes to language processing in context, but equally important are the left medial and bilateral prefrontal cortices.     

Body-part-specific representations of semantic noun categories

Word meaning processing in the brain involves ventrolateral temporal cortex, but a semantic contribution of the dorsal stream, especially frontocentral sensorimotor areas, has been controversial. We here examine brain activation during passive reading of object-related nouns from different semantic categories, notably animal, food, and tool words, matched for a range of psycholinguistic features. Results show ventral stream activation in temporal cortex along with category-specific activation patterns in both ventral and dorsal streams, including sensorimotor systems and adjacent pFC. Precentral activation reflected action-related semantic features of the word categories. Cortical regions implicated in mouth and face movements were sparked by food words, and hand area activation was seen for tool words, consistent with the actions implicated by the objects the words are used to speak about. Furthermore, tool words specifically activated the right cerebellum, and food words activated the left orbito-frontal and fusiform areas. We discuss our results in the context of category-specific semantic deficits in the processing of words and concepts, along with previous neuroimaging research, and conclude that specific dorsal and ventral areas in frontocentral and temporal cortex index visual and affective-emotional semantic attributes of object-related nouns and action-related affordances of their referent objects.     

Brain regions involved in verbal or non-verbal aspects of facial emotion recognition

To depict the neural substrates for facial emotion recognition and to determine whether their activation is confounded by a verbal factor, we studied eight normal volunteers with functional magnetic resonance imaging (fMRI). Verbal and non-verbal sample stimuli were used in a facial emotion matching task and a gender matching task (control condition). Compared with the gender tasks, the emotion tasks significantly activated the right ventral prefrontal cortex, the right lingual cortex, and the left lateral fusiform cortex, irrespective of sample stimuli. The visual association cortices showed a significant interaction between the task and the material presented, as the activation for verbal materials was higher than for non-verbal materials during the emotion matching tasks. By contrast, no significant interaction was found in the right ventral prefrontal cortex. These results suggest that the verbal factor has a different effect on the neural networks for facial emotion, processing.