Biomedical subjects

M Petrides

Publications and source records attributed to M Petrides.

At least 37 records · Page 2Linked to original sources

PubMed2000

Orbitofrontal sulci of the human and macaque monkey brain.

The present study investigated the orbitofrontal sulci in 100 normal adult human cerebral hemispheres by using magnetic resonance images that were transformed into the standardized proportional stereotaxic space most commonly used, that of Talairach and Tournoux (Talairach and Tournoux [1988]. Co-planar stereotaxic atlas of the human brain. New York: Thieme). The patterns formed by the individual sulci were then examined and compared with those of the less convoluted macaque monkey brain. Four sulci forming a similar sulcal pattern were identified in both species. The olfactory sulcus occupies the most medial position forming the lateral border of the gyrus rectus. Lateral to this, the medial, lateral, and transverse orbital sulci form a pattern often resembling an "H," "X," or "K." These sulci divide the orbitofrontal cortex into four major gyri: the medial, lateral, anterior, and posterior orbital gyri. Three major types of sulcal pattern were identified in both species based on the arrangement of these orbital sulci. Additional sulci were observed in the human brain, creating more complex patterns. Probability maps were constructed for the four main orbitofrontal sulci of the human brain. These maps provide a statistical description of the variability of the location of the orbitofrontal sulci within the three-dimensional coordinate system of Talairach and Tournoux (Talairach and Tournoux [1988]. Co-planar stereotaxic atlas of the human brain. New York: Thieme). Because these maps may be directly compared with any image transformed into the same standardized space, they provide a valuable tool for identifying and describing the location of functional or structural changes in the orbitofrontal region of the human brain.

Adult↗

PubMed2000

Architectonic analysis of the human retrosplenial cortex.

The architecture of the macaque retrosplenial cortex, including its posteroventral extension around and below the splenium of the corpus callosum, was recently characterized (Morris et al. [1999a] Eur. J. Neurosci. 11:2506-2518.). This analysis was made possible by sectioning the posterior cingulate gyrus radially, i.e., in planes that were orthogonal to its line of curvature and that, therefore, preserved the laminar organization of this region. The aim of the present study was to examine the architecture and the limits of the human retrosplenial cortex. Cross sections through the entire posterior cingulate gyrus were obtained by applying the sectioning technique developed in the monkey, so that an explicit comparison could be made between the architecture of the human and the monkey retrosplenial cortex. The present analysis revealed that, as is the case in the macaque brain, the human retrosplenial cortex is composed of granular areas 29a-c and d, and dysgranular/agranular area 30. The human retrosplenial cortex, like that of the macaque monkey, runs, as an arch, around the splenium of the corpus callosum. In the macaque brain, the retrosplenial cortex remains buried within the callosal sulcus throughout its entire course around the splenium. In the human brain, however, the posteroventral segment of the retrosplenial cortex extends on the medial wall of the cerebral hemisphere to encompass most of the cortical region commonly referred to as the "isthmus of the cingulate gyrus."

Adult↗

PubMed2000

Selectivity of the spatial learning deficit after lesions of the mammillary region in rats.

Rats with lesions of the mammillary region (MB-R) or a control group (C) were trained on a visual-spatial conditional associative learning task in which they had to learn to go to one of two locations depending on the particular visual cue presented on each trial; the rats approached the cues from different directions. The animals were subsequently tested on a spatial working memory task, the eight-arm radial maze. Rats with damage to the MB-R were able to acquire the conditional associative task at a rate comparable to that of the C animals. By contrast, lesions of the MB-R led to a severe impairment on the radial maze. The present finding of a dissociation between the effects of MB-R lesions on two different classes of behavior suggest that the spatial learning deficit following damage of this region may be specific to remembering one or more places over a given time but not the ability to form associations between visual and spatial stimuli.

Animals↗

PubMed2000

Activity in ventrolateral and mid-dorsolateral prefrontal cortex during nonspatial visual working memory processing: evidence from functional magnetic resonance imaging.

Whole-brain functional magnetic resonance imaging was used to study five healthy human subjects while they performed two nonspatial visual working memory tasks and one control task. In the first memory task, the subjects were required to view a sequence of three pattern stimuli, randomly selected from a familiar set of four stimuli, and then identify which one of three simultaneously presented stimuli was the one that had not been presented in the previous array. In the other task, the subjects were required to observe an identical sequence of three randomly selected pattern stimuli and then to respond by selecting those same stimuli in the order presented. In comparison to a baseline control task, increases in signal intensity were observed, bilaterally, in the mid-dorsolateral frontal cortex and in the right ventrolateral frontal cortex in both memory tasks. When the two tasks were compared directly, however, the first memory task, which had the higher monitoring requirement, yielded significantly greater signal intensity changes in area 9/46 of the right mid-dorsolateral frontal cortex. These results provide further evidence for the precise functional contribution made by the mid-dorsolateral frontal cortex in visual working memory tasks and concur closely with findings in nonhuman primates.

Adult↗

PubMed2000

The role of the mid-dorsolateral prefrontal cortex in working memory.

Recent studies with nonhuman primates have shown that lesions of the mid-dorsolateral prefrontal cortex, which extends from the lip of the dorsal bank of the sulcus principalis to the midline (i.e., dorsal area 46 and 9/46 and area 9), give rise to severe and long-lasting impairments on self-ordered and externally ordered tasks designed to tax executive processing within working memory, rather than short-term memory per se. Lesions limited to area 9 give rise to a mild impairment on these tasks. Thus, the mid-dorsolateral prefrontal region has been shown to be critical for the monitoring of multiple events in working memory. The mid-dorsolateral prefrontal region receives visuospatial input from the posterior dorsolateral region (areas 8 and 6) and from the cortex within the middle part (sulcal area 46) and the caudal part (area 8) of the sulcus principalis. Nonspatial visual input originates from the ventrolateral prefrontal cortex. Thus, lesions focused on the middle to caudal part of the sulcus principalis would affect visuospatial input, but would not affect the flow of nonspatial visual object information that reaches the mid-dorsolateral prefrontal region from the ventrolateral prefrontal cortex. Lesions of the sulcus principalis produce a spatially selective impairment, whereas lesions of the mid-dorsolateral prefrontal region produce a more general impairment of the monitoring and manipulation of information in working memory. The results of recent functional neuroimaging studies with human subjects are consistent with the above findings from work with the monkey.

Animals↗

PubMed2000

Orbitofrontal involvement in the processing of unpleasant auditory information.

Although little is known about the contribution of the orbitofrontal cortex to the processing of new information in man, lesion studies in monkeys have suggested that it plays a critical role. The present study investigated changes in cerebral blood flow with positron emission tomography in normal human subjects during exposure to unpleasant auditory stimuli. The results indicated that the caudal orbitofrontal cortex, area 13, which is powerfully linked to the medial temporal limbic region and is involved in the regulation of autonomic responses, is a key part of the frontal cortex responding in the face of unpleasant incoming information.

Acoustic Stimulation↗

PubMed2000

Impairments in working memory after frontal cortical excisions.

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Frontal Lobe↗

PubMed1999

Localization of cerebral activity during simple singing.

Cerebral blood flow (CBF) was measured with PET during rudimentary singing of a single pitch and vowel, contrasted to passive listening to complex tones. CBF increases in cortical areas related to motor control were seen in the supplementary motor area, anterior cingulate cortex, precentral gyri, anterior insula (and the adjacent inner face of the precentral operculum) and cerebellum, replicating most previously seen during speech. Increases in auditory cortex were seen within right Heschl's gyrus, and in the posterior superior temporal plane (and the immediately overlying parietal cortex). Since cortex near right Heschl's has been linked to complex pitch perception, its asymmetric activation here may be related to analyzing the fundamental frequency of one's own voice for feedback-guided modulation.

Adult↗

PubMed1999

Localization of cerebral activity during simple singing.

Adult↗

PubMed1999

Fiber system linking the mid-dorsolateral frontal cortex with the retrosplenial/presubicular region in the rhesus monkey.

The present study investigated the origin, course, and terminations of the association fiber system linking the frontal cortex with the hippocampal system by means of the cingulum bundle. Injections of tritiated amino acids were placed within individual cytoarchitectonic areas of the frontal cortex in the rhesus monkey. It was demonstrated that the mid-dorsolateral frontal cortex (areas 46, 9/46, and 9) and its medial extension (medial areas 9 and 9/32) is the origin of a specific fiber pathway, running posteriorly as part of the cingulum bundle, and terminating mainly in the retrosplenial area 30 and the posterior presubiculum. This fiber bundle therefore provides the anatomical substrate of a functional interaction between the mid-dorsolateral frontal cortex and the hippocampal memory system for the monitoring of information within working memory.

Animals↗

PubMed1999

Human cortical gustatory areas: a review of functional neuroimaging data.

In an effort to define human cortical gustatory areas we reviewed functional neuroimaging data for which coordinates standardized in Talairach proportional space were available. We observed a wide distribution of peaks within the insula and parietal and frontal opercula, suggesting multiple gustatory regions within this cortical area. Multiple peaks also emerged in the orbitofrontal cortex. However, only two peaks, both in the right hemisphere, were observed in the caudolateral orbitofrontal cortex, the region likely homologous to the secondary taste area described in monkeys. Overall significantly more peaks originated from the right hemisphere suggesting asymmetrical cortical representation of taste favoring the right hemisphere.

Brain Mapping↗

PubMed1999

Three-dimensional MRI atlas of the human cerebellum in proportional stereotaxic space.

We have prepared an atlas of the human cerebellum using high-resolution magnetic resonance-derived images warped into the proportional stereotaxic space of Talairach and Tournoux. Software that permits simultaneous visualization of the three cardinal planes facilitated the identification of the cerebellar fissures and lobules. A revised version of the Larsell nomenclature facilitated a simple description of the cerebellum. This atlas derived from a single individual was instrumental in addressing longstanding debates about the gross morphologic organization of the cerebellum. It may serve as the template for more precise identification of cerebellar topography in functional imaging studies in normals, for investigating clinical-pathologic correlations in patients, and for the development of future probabilistic maps of the human cerebellum.

Cerebellum↗

PubMed1999

Increased blood flow in the basal ganglia when using cues to direct attention.

We used positron emission tomography (PET) in ten subjects to study the brain regions involved in voluntary shifts of attention. For six scans, subjects performed a visual target detection task in which the location of the target was indicated in advance on some proportion of trials by the appearance of an arrow cue at fixation. The informative cues were successful in speeding reaction time to the target. Blood flow in the left putamen was correlated with the proportion of informative cues provided within a scan. We discuss this finding in terms of three possible interpretations: attentional shifts, response inhibition, and motor preparation related to the use of the right hand to respond. Blood flow in cortical regions commonly associated with attention was not related to cue ratio, a finding that may reflect automatization of the processes involved in interpreting and using the cues.

Adult↗

PubMed1999

Ibotenic acid lesions of the basolateral, but not the central, amygdala interfere with conditioned taste aversion: evidence from a combined behavioral and anatomical tract-tracing investigation.

Rats (Rattus norvegicus) with almost complete ibotenic acid lesions (at least 90%) of the basolateral amygdaloid complex (BLA) failed to learn a conditioned taste aversion (CTA; Experiment 1A). In these same BLA rats, the bidirectional parabrachial-insular pathway that courses through the central nucleus of the amygdala (Ce) was shown to be spared (Experiment 1B), indicating that the BLA per se is critical for CTA learning. In contrast to the deleterious effect of BLA lesions on CTA, ibotenic acid lesions of the Ce did not block CTA learning (Experiment 2). Nonreinforced preexposure to the gustatory stimulus attenuated CTA acquisition in normal rats, and, under these conditions, rats with BLA lesions were no longer impaired (Experiment 3). Thus, ibotenic acid lesions centered over the Ce, sparing a considerable extent of the BLA, together with the testing procedure used in previous experiments (e.g., L. T. Dunn & B. J. Everitt, 1988), led to the belief that the CTA deficits reported after electrolytic lesions of the amygdala were the result of incidental damage to fibers of passage.

Amygdala↗

PubMed1999

The effects of lesions to the anterior thalamic nuclei on object-place associations in rats.

Rats with lesions of the anterior nuclei of the thalamus were trained postoperatively on two spatial conditional associative learning tasks. In the first task, the rats were required to choose one or the other of two objects depending on the location in which they were found. In the second task, the animals learned to turn left or right depending on which one of two visual cues was presented. A third experiment examined the effects of damage to the anterior thalamic nuclei on the eight-arm radial maze, a spatial working memory task. Damage of the anterior thalamic nuclei impaired performance on the radial maze task and the conditional task requiring associations between objects and their location. By contrast, rats with anterior thalamic lesions were able to acquire, at a rate comparable with that of operated control animals, the conditional task requiring associations between objects and body turns. These findings suggest that lesions to the anterior thalamic nuclei result in a general impairment in learning about allocentric spatial information without disrupting the learning of egocentric spatial information.

Animals↗

PubMed1999

Redefining the functional organization of working memory processes within human lateral prefrontal cortex.

It is widely held that the frontal cortex plays a critical part in certain aspects of spatial and non-spatial working memory. One unresolved issue is whether there are functionally distinct subdivisions of the lateral frontal cortex that subserve different aspects of working memory. The present study used positron emission tomography (PET) to demonstrate that working memory processes within the human mid-dorsolateral and mid-ventrolateral frontal regions are organized according to the type of processing required rather than according to the nature (i.e. spatial or non-spatial), of the information being processed, as has been widely assumed. Two spatial working memory tasks were used which varied in the extent to which they required different executive processes. During a 'spatial span' task that required the subject to hold a sequence of five previously remembered locations in working memory a significant change in blood-flow was observed in the right mid-ventrolateral frontal cortex, but not in the anatomically and cytoarchitectonically distinct mid-dorsolateral frontal-lobe region. By contrast, during a '2-back' task that required the subject to continually update and manipulate an ongoing sequence of locations within working memory, significant blood flow increases were observed in both mid-ventrolateral and mid-dorsolateral frontal regions. When the two working memory tasks were compared directly, the one that emphasized manipulation of information within working memory yielded significantly greater activity in the right mid-dorsolateral frontal cortex only. This dissociation provides unambiguous evidence that the mid-dorsolateral and mid-ventrolateral frontal cortical areas make distinct functional contributions to spatial working memory and corresponds with a fractionation of working memory processes in psychological terms.

Adult↗

PubMed1999

Dorsolateral prefrontal cortex: comparative cytoarchitectonic analysis in the human and the macaque brain and corticocortical connection patterns.

The cytoarchitecture of the human and the macaque monkey dorsolateral prefrontal cortex has been examined in a strictly comparative manner in order to resolve major discrepancies between the available segmentations of this cortical region in the human and the monkey brain. In addition, the connections of the dorsolateral prefrontal cortical areas were re-examined in the monkey. The present analysis showed that only a restricted portion of what had previously been labelled as area 46 in the monkey has the same characteristics as area 46 of the human brain; the remaining part of this monkey region has the characteristics of a portion of the middle frontal gyrus in the human brain that had previously been included as part of area 9. We have labelled this cortical area as 9/46 in both species. These two areas (i.e. 46 and 9/46), which constitute the lower half of the mid-dorsolateral frontal cortex, have a well-developed granular layer IV, and can easily be distinguished from area 9, on the upper part of the mid-dorsolateral region, which does not have a well-developed granular layer IV. Area 9 has the same basic pattern of connections as areas 46 and 9/46, but, unlike the latter areas, it does not receive input from the lateral parietal cortex. Caudal to area 9, on the dorsomedial portion of the frontal cortex, there is a distinct strip of cortex (area 8B) which, unlike area 9, receives significant input from the prestriate cortex and the medial parietal cortex. The present results provide a basis for a closer integration of findings from functional neuroimaging studies in human subjects with experimental work in the monkey.

Animals↗

PubMed1999

Architecture and connections of retrosplenial area 30 in the rhesus monkey (Macaca mulatta).

Because of the sharp curvature of the retrosplenial region around the splenium of the corpus callosum, standard coronal sections are not appropriate for architectonic analysis of its posteroventral part. In the present study, examination of the posteroventral retrosplenial region of the rhesus monkey in sections that were orthogonal to its axis of curvature (and therefore appropriate for architectonic analysis) has permitted definition of its architecture and precise extent. This analysis demonstrated that areas 29 and 30 of the retrosplenial cortex, as well as adjacent area 23 of the posterior cingulate cortex, extend together as an arch around the splenium of the corpus callosum and maintain their topographical relationship with one another throughout their entire course. Injections of anterograde and retrograde tracers confined to retrosplenial area 30 revealed that this area has reciprocal connections with adjacent areas 23, 19 and PGm, with the mid-dorsolateral part of the prefrontal cortex (areas 9, 9/46 and 46), with multimodal area TPO in the superior temporal sulcus, as well as the posterior parahippocampal cortex, the presubiculum and the entorhinal cortex. There are also bidirectional connections with the lateroposterior thalamic nucleus, as well as the laterodorsal and the anteroventral limbic thalamic nuclei. The connectivity of area 30 suggests that it may play a role in working memory processes subserved by the mid-dorsolateral frontal cortex in interaction with the hippocampal system.

Animals↗