Biomedical subjects

D N Pandya

Publications and source records attributed to D N Pandya.

At least 19 recordsLinked to original sources

PubMed2006

Efferent association pathways originating in the caudal prefrontal cortex in the macaque monkey.

The efferent association fibers from the caudal part of the prefrontal cortex to posterior cortical areas course via several pathways: the three components of the superior longitudinal fasciculus (SLF I, SLF II, and SLF III), the arcuate fasciculus (AF), the fronto-occipital fasciculus (FOF), the cingulate fasciculus (CING F), and the extreme capsule (Extm C). Fibers from area 8Av course via FOF and SLF II, merging in the white matter of the inferior parietal lobule (IPL) and terminating in the caudal intraparietal sulcus (IPS). A group of these fibers turns ventrally to terminate in the caudal superior temporal sulcus (STS). Fibers from the rostral part of area 8Ad course via FOF and SLF II to the IPS and IPL and via the AF to the caudal superior temporal gyrus and STS. Some fibers from the rostral part of area 8Ad are conveyed to the medial parieto-occipital region via FOF, to the STS via Extm C, and to the caudal cingulate gyrus via CING F. Fibers from area 8B travel via SLF I to the supplementary motor area and area 31 in the caudal dorsal cingulate region and via the CING F to cingulate areas 24 and 23 and the cingulate motor areas. Fibers from area 9/46d course via SLF I to the superior parietal lobule and medial parieto-occipital region, via SLF II to the IPL. Fibers from area 9/46v travel via SLF III to the rostral IPL and the frontoparietal opercular region and via the CING F to the cingulate gyrus.

Amino Acids↗

PubMed2004

Cytoarchitecture and cortical connections of the posterior cingulate and adjacent somatosensory fields in the rhesus monkey.

The cytoarchitecture and connections of the caudal cingulate and medial somatosensory areas were investigated in the rhesus monkey. There is a stepwise laminar differentiation starting from retrosplenial area 30 towards the isocortical regions of the medial parietal cortex. This includes a gradational emphasis on supragranular laminar organization and general reduction of the infragranular neurons as one proceeds from area 30 toward the medial parietal regions, including areas 3, 1, 2, 5, 31, and the supplementary sensory area (SSA). This trend includes a progressive increase in layer IV neurons. Area 23c in the lower bank and transitional somatosensory area (TSA) in the upper bank of the cingulate sulcus appear as nodal points. From area 23c and TSA the architectonic progression can be traced in three directions: one culminates in areas 3a and 3b (core line), the second in areas 1, 2, and 5 (belt line), and the third in areas 31 and SSA (root line). These architectonic gradients are reflected in the connections of these regions. Thus, cingulate areas (30, 23a, and 23b) are connected with area 23c and TSA on the one hand and have widespread connections with parieto-temporal, frontal, and parahippocampal (limbic) regions on the other. Area 23c has connections with areas 30, 23a and b, and TSA as well as with medial somatosensory areas 3, 1, 2, 5, and SSA. Area 23c also has connections with parietotemporal, frontal, and limbic areas similar to areas 30, 23a, and 23b. Area TSA, like area 23c, has connections with areas 3, 1, 2, 5, and SSA. However, it has only limited connections with the parietotemporal and frontal regions and none with the parahippocampal gyrus. Medial area 3 is mainly connected to medial and dorsal sensory areas 3, 1, 2, 5, and SSA and to areas 4 and 6 as well as to supplementary (M2 or area 6m), rostral cingulate (M3 or areas 24c and d), and caudal cingulate (M4 or areas 23c and d) motor cortices. Thus, in parallel with the architectonic gradient of laminar differentiation, there is also a progressive shift in the pattern of corticocortical connections. Cingulate areas have widespread connections with limbic, parietotemporal, and frontal association areas, whereas parietal area 3 has more restricted connections with adjacent somatosensory and motor cortices. TSA is primarily related to the somatosensory-motor areas and has limited connections with the parietotemporal and frontal association cortices.

Animals↗

PubMed2002

Comparative cytoarchitectonic analysis of the human and the macaque ventrolateral prefrontal cortex and corticocortical connection patterns in the monkey.

A comparison of the cytoarchitecture of the human and the macaque monkey ventrolateral prefrontal cortex demonstrated a region in the monkey that exhibits the architectonic characteristic of area 45 in the human brain. This region occupies the dorsal part of the ventrolateral prefrontal convexity just below area 9/46v. Rostroventral to area 45 in the human brain lies a large cortical region labelled as area 47 by Brodmann. The ventrolateral component of this region extending as far as the lateral orbital sulcus has architectonic characteristics similar to those of the ventrolateral prefrontal region labelled by Walker as area 12 in the macaque monkey. We designated this region in both the human and the monkey ventrolateral prefrontal cortex as area 47/12. Thus, area 47/12 designates the specific part of the zone previously labelled as area 47 in the human brain that has the same overall architectonic pattern as that of Walker's area 12 in the macaque monkey brain. The cortical connections of these two areas were examined in the monkey by injecting fluorescent retrograde tracers. Although both area 45 and area 47/12 as defined here had complex multimodal input, they could be differentiated in terms of some of their inputs. Retrograde tracers restricted to area 47/12 resulted in heavy labelling of neurons in the rostral inferotemporal visual association cortex and in temporal limbic areas (i.e. perirhinal and parahippocampal cortex). In contrast, injections of tracers into dorsally adjacent area 45 demonstrated strong labelling in the superior temporal gyrus (i.e. the auditory association cortex) and the multimodal cortex in the upper bank of the superior temporal sulcus.

Aged↗

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

Cortical connections of the frontoparietal opercular areas in the rhesus monkey.

The connections of the frontoparietal opercular areas were studied in rhesus monkeys by using antero- and retrograde tracer techniques. The rostral opercular cortex including the gustatory and proisocortical motor (ProM) areas is connected with precentral areas 3, 1, and 2 as well as with the rostral portion of the opercular area which resembles the second somatosensory type of cortex (area SII) and the ventral portion of area 6. Its distant connections are with the ventral portion of prefrontal areas 46, 11, 12, and 13 as well as with the rostral insula and cingulate motor area (CMAr). The mid opercular region (areas 1 and 2) is connected with pre- and postcentral areas 3, 1, and 2 as well as SII. Additionally, it is connected with the ventral portion of area 6, area 44, area ProM, the gustatory area, and the rostral insula. Its distant connections are with area 4, the ventral portion of area 46, area 7b, and area POa in the intraparietal sulcus (IPS). The rostral parietal opercular region is connected with the postcentral portions of areas 3, 1, and 2; areas 5, 7, and SII; the gustatory area; and the vestibular area. Its other connections are with area 4, area 44, the ventral portion of area 46, area ProM, CMAr, and the supplementary motor area (SMA). The caudal opercular region is connected with the dorsal portion of area 3; areas 2, 5, and 7a; and areas PEa as well as IPd of IPS. It is also connected with area SII, insula, and the superior temporal sulcus. Its distant connections are with area 44; the dorsal portion of area 8 and the ventral portion of area 46; as well as CMAr, SMA, and the supplementary sensory area. This connectivity suggests that the ventral somatosensory areas are involved in sensorimotor activities mainly related to head, neck, and face structures as well as to taste. Additionally, these areas may have a role in frontal (working) and temporal (tactile) memory systems.

Afferent Pathways↗

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↗

PubMed1998

Corticostriatal connections of the superior temporal region in rhesus monkeys.

Corticostriatal connections of auditory areas within the supratemporal plane and in rostral and caudal portions of the superior temporal gyrus were studied by the autoradiographic anterograde tracing technique. The results show that the primary auditory cortex has limited projections to the caudoventral putamen and to the tail of the caudate nucleus. In contrast, the second auditory area within the circular sulcus has connections to the rostral and the caudal putamen and to the body of the caudate nucleus and the tail. The association areas of the superior temporal gyrus collectively have widespread corticostriatal projections characterized by differential topographic distributions. The rostral part of the gyrus projects to ventral portions of the head of the caudate nucleus and of the body and to the tail. In addition, there are connections to rostroventral and caudoventral portions of the putamen. The mid-portion of the gyrus projects to similar striatal regions, but the connections to the head of the caudate nucleus are less extensive. Compared with the rostral and middle parts of the superior temporal gyrus, the caudal portion has little connectivity to the tail of the caudate nucleus. It projects more dorsally within the head and the body and also more dorsally within the caudal putamen. These differential patterns of corticostriatal connectivity are consistent with functional specialization at the cortical level.

Animals↗

PubMed1997

Corticothalamic connections of extrastriate visual areas in rhesus monkeys.

Corticothalamic connections of extrastriate visual areas were studied by using the autoradiographic anterograde tracing technique. The results show that the medial extrastriate region above the calcarine sulcus projects mainly to the lateral pulvinar (PL), medial pulvinar (PM), and lateral posterior (LP) nuclei. In addition, the dorsal portion of the medial region has connections to the lateral dorsal (LD) as well as to intralaminar nuclei. The dorsolateral extrastriate region projects strongly to the PL and LP nuclei, to the PM and inferior pulvinar (PI) nuclei, and to the LD and intralaminar nuclei. The lateral extrastriate region above the inferior occipital sulcus (IOS) has strong connections to both the PL and PI nuclei and has minor projections to the PM and oral pulvinar nuclei. The ventrolateral extrastriate region below the IOS projects mainly to the PI nucleus and to the caudal portion of the PL nucleus and has some projections to the PM nucleus. The ventromedial extrastriate region medial to the occipitotemporal sulcus has strong connections with the ventral and medial sectors of the PI nucleus. This region also projects to the caudal portion of the PL nucleus and has minor connections to the LP nucleus. Finally, the annectant gyrus projects to the PL nucleus and to the rostral portion of the PI nucleus and has minor connections to the PM nucleus. Thus, the medial and dorsolateral extrastriate regions are related mainly to the PL and LP nuclei as well as to intralaminar nuclei. In contrast, the ventrolateral and ventromedial regions are connected strongly with the PI nucleus. This connectional organization appears to reflect functional differentiation at the cortical level.

Animals↗

PubMed1997

Anatomic organization of the basilar pontine projections from prefrontal cortices in rhesus monkey.

In our ongoing attempt to determine the anatomic substrates that could support a cerebellar contribution to cognitive processing, we investigated the prefrontal cortical projections to the basilar pons. A detailed understanding of these pathways is needed, because the prefrontal cortex is critical for a number of complex cognitive operations, and the corticopontine projection is the obligatory first step in the corticopontocerebellar circuit. Prefrontopontine connections were studied using the autoradiographic technique in rhesus monkey. The pontine projections were most prominent and occupied the greatest rostrocaudal extent of the pons when derived from the dorsolateral prefrontal convexity, including areas 8Ad, 9/46d, and 10. Lesser pontine projections were observed from the medial prefrontal convexity and area 45B in the inferior limb of the arcuate sulcus. In contrast, ventral prefrontal and orbitofrontal cortices did not demonstrate pontine projections. The prefrontopontine terminations were located preferentially in the paramedian nucleus and in the medial parts of the peripeduncular nucleus, but each cortical area appeared to have a unique complement of pontine nuclei with which it is connected. The existence of these corticopontine pathways from prefrontal areas concerned with multiple domains of higher-order processing is consistent with the hypothesis that the cerebellum is an essential node in the distributed corticosubcortical neural circuits subserving cognitive operations.

Animals↗

PubMed1997

Morphometry of in vivo human white matter association pathways with diffusion-weighted magnetic resonance imaging.

The precise characterization of cortical connectivity is important for the understanding of brain morphological and functional organization. Such connectivity is conveyed by specific pathways or tracts in the white matter. Diffusion-weighted magnetic resonance imaging detects the diffusivity of water molecules in three dimensions. Diffusivity is anisotropic in oriented tissues such as fiber tracts. In the present study, we used this method to map (in terms of orientation, location, and size) the "stem" (compact portion) of the principal association, projection, and commissural white matter pathways of the human brain in vivo, in 3 normal subjects. In addition, its use in clinical neurology is illustrated in a patient with left inferior parietal lobule embolic infarction in whom a significant reduction in relative size of the stem of the left superior longitudinal fasciculus was observed. This represents an important method for the characterization of major association pathways in the living human that are not discernible by conventional magnetic resonance imaging. In the clinical domain, this method will have a potential impact on the understanding of the diseases that involve white matter such as stroke, multiple sclerosis, amyotrophic lateral sclerosis, head injury, and spinal cord injury.

Cerebral Cortex↗

PubMed1997

The cerebrocerebellar system.

If there is a cerebellar contribution to nonmotor function, particularly to cognitive abilities and affective states, then there must be corresponding anatomic substrates that support this. The cerebellum is strongly interconnected with the cerebral hemispheres in both feedforward (cerebral hemispheres to cerebellum) and feedback directions. This relationship has long been recognized, particularly with respect to the motor and sensory cortices. Investigations performed over the last decade however, have demonstrated for the first time the organization and strength of the connections that link the cerebellum with areas of the cerebral cortex known to be concerned with higher order behavior rather than with motor control. The feedforward projections from these higher order areas, namely the associative and paralimbic cortices, seem to be matched, at least in the limited but definite demonstrations to date, by cerebellar projections back to these same areas. These observations are important because they are congruent with the notion that cognitive functions are distributed among multiple cortical and subcortical nodes, each of which functions in concert but in a unique manner to produce an ultimate behavior pattern. This chapter describes the neural circuitry postulated to subserve the cerebellar contribution to nonmotor processing, particularly cognitive and affective modulation, and discusses the theoretical implications of these anatomic findings.

Affect↗

PubMed1996

Comparison of prefrontal architecture and connections.

The advent of new technology has led to a proliferation of studies examining the functional roles of discrete prefrontal cortical areas. This has created a need for more precise information regarding the morphological characteristics of this region. Existing architectonic maps of human and monkey brains are not compatible with regard to areal delineations and topography, creating significant difficulty in interpreting comparative data. Therefore, we have re-examined the comparative morphological organization of the prefrontal cortex in humans and rhesus monkeys. Our analysis indicates that the architectonic areas in both species correspond in terms of morphological features as well as topographical locations. We have developed a common organizational schema for these areas, thereby allowing for a resolution of previous discrepancies. Moreover, in monkeys a connectional analysis has revealed that each of the newly designated areas is characterized by a unique pattern of cortical relationships. The present organizational schema provides a framework for interrelating findings such as those obtained from human brain imaging studies with those from behavioural investigations of non-human primates.

Amidines↗

PubMed1995

Prefrontal cortex projections to the basilar pons in rhesus monkey: implications for the cerebellar contribution to higher function.

The feedforward limb of the cerebrocerebellar system is directed largely through the corticopontine pathway. We determined the extent to which higher order corticopontine projections are derived from prefrontal associative cortices by injecting anterograde tracers into multiple prefrontal regions in rhesus monkeys. Most prefrontopontine projections were derived from the dorsolateral and dorsomedial convexities, including areas 8A, 46 dorsal, 9, and 10; and lighter projections arose from medial and ventrolateral cortices. These findings strengthen the observation that the cerebrocerebellar system incorporates associative cerebral regions, and they enhance the notion that the cerebellum participates in the organization of cognitive function.

Animals↗

PubMed1995

Corticostriatal connections of extrastriate visual areas in rhesus monkeys.

The striatal connections of extrastriate visual areas were examined by the autoradiographic technique in rhesus monkeys. The medial as well as the dorsolateral extrastriate regions project preferentially to dorsal and lateral portions of the head and of the body of the caudate nucleus, as well as to the caudodorsal sector of the putamen. The rostral portion of the annectant gyrus has connections to the caudal sector of the body and to the genu, whereas projections from the caudal portion of the lower bank of the superior temporal sulcus are directed to dorsal and central sectors of the head and the body, to the genu and the tail, as well as to the caudal putamen. The ventrolateral extrastriate region is related mainly to the ventral sector of the body, to the genu and the tail, and to the caudal putamen. In contrast, the striatal projections of the ventromedial extrastriate cortex resemble those of the medial and dorsolateral regions. The caudal inferotemporal cortex is related strongly to the tail of the caudate nucleus and to the ventral putamen. The differential corticostriatal connectivity of the various extrastriate regions may contribute to the specific functional roles of these cortices. Thus, the connections from the dorsomedial, dorsolateral, and ventromedial areas to dorsal portions of the caudate nucleus and of the putamen may serve a visuospatial function. In contrast, the connections from the ventrolateral extrastriate and inferotemporal regions to the tail of the caudate nucleus and to the ventral putamen may have a role in visual object-related processes.

Animals↗

PubMed1994

Corticothalamic connections of auditory-related areas of the temporal lobe in the rhesus monkey.

Corticothalamic connections of auditory areas of the superior temporal regions (STR) were investigated in the rhesus monkey. These connections are organized according to the recently described architectonic parcellation of the STR. The core line regions of the supratemporal plane (STP) project to the medial geniculate nucleus (MGN). All regions except the primary auditory area also have projections to additional thalamic nuclei. The rostral STP has strong connections with the caudal part of the ventral subdivision (MGv) of MGN as well as with medial pulvinar (PM). In contrast the primary auditory area projects mainly to rostral MGv. The caudalmost STP projects mainly to the dorsal subdivision (MGd) and to the magnocellular subdivision (MGmc) as well as to the PM and the lateral (PL) and oral (PO) pulvinar, nucleus limitans (Li), and mediodorsal (MD) nucleus. The belt line regions of the superior temporal gyrus (STG) project mainly to the pulvinar but also have projections to MGd and MGmc. Specifically, rostral STG projects to the caudal part of PM, to MGmc, and to the suprageniculate (SG) nucleus, whereas caudal STG projects to the rostral part of PM and to PL, PO, MGd, MGmc, SG-Li and MD nuclei. The root line areas in the circular sulcus of the Sylvian fissure project mainly to MGmc but also to MGd, PM, and SG-Li nuclei. These connections originate mainly from neurons in cortical layer VI, with some from layer Vb. It is suggested that these connections may be involved in different aspects of auditory information processing.

Animals↗

PubMed1994

Parietal, temporal, and occipital projections to cortex of the superior temporal sulcus in the rhesus monkey: a retrograde tracer study.

The afferent cortical connections of individual cytoarchitectonic areas within the superior temporal sulcus (STS) of the rhesus monkey were studied by retrograde tracer techniques, including double tracer experiments. Rostral superior temporal polysensory (STP) cortex (area TPO-1) receives input from the rostral superior temporal gyrus (STG), cortex of the circular sulcus, and parahippocampal gyrus (PHG) (areas 35, TF, and TL). Mid-STP cortex (areas TPO-2 and -3) has input from the mid-STG, cortex of the mid-circular sulcus, caudal inferior parietal lobule (IPL), cingulate gyrus (areas, 23, 24, retrosplenial cortex), and mid-PHG (areas 28, TF, TH, and TL). Caudal STP cortex (area TPO-4) has afferent connections with the caudal STG, cortex of the caudal insula and caudal circular sulcus, caudal IPL, lower bank of the intraparietal sulcus (IPS), medial parietal lobe, cingulate gyrus, and mid- and caudal PHG (areas TF, TH, TL; prostriate area). The most rostral cortex of the lower bank of the STS (areas TEa and TEm), a presumed visual association area, receives input from the rostral inferotemporal (IT) region; more caudal portions of areas TEa and TEm have afferent connections with the caudal IT region, PHG, preoccipital gyrus, and cortex of the lower bank of the IPS.

Afferent Pathways↗

PubMed1994

Laminar origin of striatal and thalamic projections of the prefrontal cortex in rhesus monkeys.

Prefrontostriatal and prefrontothalamic connections in rhesus monkeys have been shown to be organized in a topographic manner. These projections originate largely from infragranular layers V and VI. To examine whether the striatal and thalamic connections from the prefrontal cortex arise from separate neuronal populations or are collateralized, two different fluorescent retrograde tracers (diamidino yellow and fast blue) were injected into topographically similar regions of the head of the caudate nucleus and the mediodorsal nucleus in the same animal. The results show that although prefrontostriatal and prefrontothalamic projections arise from similar topographic regions, their laminar origins are distinctive. The connections to the head of the caudate nucleus originate mainly from layer Va, to a lesser extent from layer Vb, with a minor contribution from layers III and VI. In contrast, the projections to the mediodorsal nucleus emanate largely from layer VI, and also from layer Vb. Only occasional double-labeled neurons were observed, indicating that prefrontostriatal and prefrontothalamic connections originate from separate neuronal populations. The differential laminar distributions of neurons projecting to the head of the caudate nucleus and the mediodorsal nucleus suggest that these structures may receive independent types of information from the prefrontal cortex.

Amidines↗