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PubMed1982

Spatial memory impairments following damage to the mediodorsal nucleus of the thalamus in rhesus monkeys.

The present study assessed whether the mediodorsal nucleus (MD) of the primate thalamus subserves some of the same learning and memory functions mediated by its prefrontal cortical projection areas. Behavioral effects of MD lesions were evaluated in 14 young adult rhesus monkeys, using tests known to be sensitive to damage in different regions of the prefrontal cortex. Performance on a spatial delayed alternation task was significantly (P less than 0.01) impaired by MD lesions, and this impairment was significantly correlated (rs = 0.52) with damage to the posterior half of the mediodorsal nucleus. Such damage was also correlated significantly (rs = 0.51) with performance on another spatial memory task, delayed response; monkeys that sustained the largest lesions of the posterior mediodorsal nucleus were significantly (P less than 0.05) impaired on this task relative to operated animals suffering the least posterior MD damage. In contrast to their performance on spatial memory tasks, operated animals were not impaired on tests of object reversal or visual pattern discrimination. These results indicate that lesions of the mediodorsal nucleus can elicit a specific syndrome of spatial memory loss qualitatively similar to that observed after damage to the dorsolateral prefrontal cortex.

Animals↗

PubMed2003

Regional specificity in the neuropathologic substrates of schizophrenia: a morphometric analysis of Broca's area 44 and area 9.

BACKGROUND: Numerous recent studies of postmortem schizophrenic brains have reported the presence of structural abnormalities in the dorsolateral prefrontal cortex (dlPFC) that are consistent with a reduction of neuropil. Ventrolateral prefrontal areas have been studied less extensively, and therefore it is not clear whether these cortices exhibit pathologic abnormalities of the same type and magnitude. Because thought disturbances in schizophrenic patients involve language processing, we have performed a morphometric analysis of Broca's area in the ventral frontal lobe. METHODS: Neuronal and glial density and somal size were assessed via stereologic cell counting in postmortem samples of Broca's area 44 in 9 schizophrenic patients and 14 normal controls. Cell density was reexamined in dorsolateral prefrontal area 9 as an internal control. RESULTS: We did not detect abnormalities in overall or laminar neuronal density, glial density, cortical thickness, or somal size in area 44 of schizophrenic patients. In contrast, neuronal density in area 9 exhibited a 12% increase in the schizophrenic cohort, replicating previous findings. In addition, there was a significant effect of disease on laminar neuronal density in area 9, with neuronal density tending to be higher (7%-29%) in all layers. CONCLUSIONS: The absence of significant cytoarchitectonic abnormalities in Broca's area in the same brains in which the dlPFC exhibited an increase in neuronal density suggests that the neuropil deficit is a regionally specific pathologic finding in schizophrenia and indicates that the dlPFC is a particularly vulnerable target of the disease process.

Adult↗

PubMed1991

Cytoarchitecture and intrafrontal connections of the frontal cortex of the brain of the hamadryas baboon (Papio hamadryas).

A study was made of the cytoarchitecture of the lateral and medial frontal cortex in the hamadryas baboon (Papio hamadryas). The frontal cortico-cortical connections of areas 46, 8, 6, and 4 were investigated by injection of wheat-germ agglutinine conjugated to horseradish peroxiase (WGA-HRP) into different regions of areas 46, 8, and 6. The lateral region of the frontal lobe of the baboon consists of broad areas of motor (area 4), premotor (area 6), and the dorsolateral prefrontal cortex, each of which is further divided into subdivisions with distinct cytoarchitectural features: areas 4a, 4b, 4c; 6 a alpha, 6a beta, 6a gamma, and 6b beta; 8A and 8B; 45; 46 and 46ps; 9; 10; and 12. Although the frontal cortex of the baboon brain exhibits the same basic cytoarchitectural features as the frontal corticies of the cercopithecus (campbelli?) (Vogt and Vogt, '19) or the macaque (Walker, '40; Barbas and Pandya, '87, '89), the baboon frontal cortex is very different from that of the macaque and cercopithecus in terms of cytoarchitecture: (1) the baboon frontal cortex has an additional area, termed here "6a gamma", within area 6, which has cytoarchitectural characteristics that are intermediate between those of areas 6 and 8; (2) the aggregation of giant pyramidal cells (greater than 50 microns in diameter) is found only in area 4a in the baboon, whereas such aggregates are found in areas 4a and 4b and, occasionally, in area 4c in the macaque; and (3) area 46 of the prefrontal cortex of the baboon can be subdivided into the cortex that surrounds the principal sulcus (area 46) and the upper and lower banks of the principal sulcus (area 46ps). Retrogradely WGA-HRP labeled cells and anterogradely WGA-HRP labeled terminals coexisted in the frontal cortex in a columnar fashion, indicative of a reciprocity among the connections. The frontal cortico-cortical connections of areas 46, 8, 6, and 4 in the hamadryas baboon were organized as follows: (1) areas 46, 8, and 6 were connected to one another, (2) area 4 was connected only to area 6, and (3) these connections showed a gross ventrodorsal topography: the ventral regions of each of areas 46, 8, and 6 were connected more strongly to the ventral than the dorsal regions of the other areas; the dorsal regions of each of areas 46, 8, and 6 were connected more strongly to the dorsal than the ventral regions of the other areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1992

Cortical connections of subdivisions of inferior temporal cortex in squirrel monkeys.

Patterns of cortical connections and architectonics were used to determine subdivisions of inferior temporal (IT) cortex of squirrel monkeys. Single or multiple injections of the tracers wheat germ agglutinin-horseradish peroxidase, Fast Blue, Diamidino Yellow, Fluoro-Gold, and 3H-amino acids were placed into IT cortex. Most injections were placed in caudal IT cortex in the region previously shown to receive input from the caudal subdivision of the Dorsolateral Area, DLC; additional injections were placed in more rostral IT cortex. The results indicate the presence of two major regions: a caudal region, ITC, and a rostral region, ITR. An intermediate region of cortex along the ITC-ITR border that displays some connections of ITC and some connections of ITR may be another area. ITC contains a more myelinated dorsal area, ITCd, and a larger ventral area, ITCv. Both ITCd and ITCv receive a major projection from DLC; additional input from DLR, MT, and VII; and send strong projections to ITR, the lateral bank of the superior temporal sulcus, and dorsolateral prefrontal cortex. Only ITCd has strong connections with DLR and cortex in the depths of the superior temporal sulcus, and only ITCv has connections with lateral orbital cortex. The overall pattern of connections between ITC and DLC suggests that ITC has a crude topographic organization, with dorsal cortex representing the lower field and ventral cortex representing the upper field. ITR differs from ITC by receiving little if any input from DLC; projecting to inferior temporal polar cortex, the rostral Sylvian fissure, and medial orbital cortex; and having a less distinct layer IV. Comparison of subdivisions of inferior temporal cortex defined in the present study in squirrel monkeys and those reported in other primates suggests that ITC of squirrel monkeys may correspond to area TEO of macaque monkeys.

Animals↗

PubMed2005

Dissociation of neural systems mediating shifts in behavioral response and cognitive set.

The ability to generate appropriate behaviors in response to changing situations requires both the alteration of ongoing behavior and the understanding of the global rules governing stimulus categorization in a given context. Neuropsychological tests that have been developed to measure this form of cognitive flexibility, such as the Wisconsin Card Sorting Test, have reliably demonstrated that individuals with lesions in regions of the prefrontal cortex and basal ganglia have difficulty generating a cognitive set and altering rule-governed behavior. Recent neuroimaging studies have supported the role of these brain regions in the performance of response shifting and cognitive set shifting. However, the precise role of these regions in the individual components of these tasks remains a contentious issue. Here, we used event-related functional magnetic resonance imaging (fMRI) to dissociate the neural circuitry involved in the alteration of ongoing behavior and the shifting of cognitive set. Participants viewed geometric shapes as they appeared individually in rapid succession and responded with an appropriate button press based upon whether the individual shape was a predetermined target stimulus. Responses were required for each shape presented. The fMRI results indicated that response shifting specifically activated a dorsal neural circuit comprised of the dorsolateral prefrontal cortex, anterior cingulate, and intraparietal sulcus. Shifts in cognitive set were mediated by ventrolateral prefrontal cortex, anterior cingulate, and striatum. These findings suggest that the alteration of ongoing behavior and shifting of cognitive set are mediated by two distinct neural systems interconnected by the anterior cingulate.

Adult↗

PubMed2000

Intrinsic excitatory connections in the prefrontal cortex and the pathophysiology of schizophrenia.

Working memory, a fundamental cognitive process that is disturbed in schizophrenia, appears to depend upon the sustained activity of specific populations of neurons in the prefrontal cortex. Understanding the neural mechanism(s) that may contribute to the sustained activity of these neurons represents a critical step in predicting the types of alterations in prefrontal circuitry that may be present in schizophrenia, and in determining how such alterations may contribute to the cognitive symptoms of this disorder. This article reviews recent findings which suggest that intrinsic horizontal connections among pyramidal neurons in layer 3 of the dorsolateral prefrontal cortex may provide a critical anatomical substrate for working memory processes, and that alterations in these connections may account for the observations of disturbed working memory, adolescence-related onset of clinical features, and certain pathological changes in the prefrontal cortex of subjects with schizophrenia.

Animals↗

PubMed2006

Disruption of right prefrontal cortex by low-frequency repetitive transcranial magnetic stimulation induces risk-taking behavior.

Decisions require careful weighing of the risks and benefits associated with a choice. Some people need to be offered large rewards to balance even minimal risks, whereas others take great risks in the hope for an only minimal benefit. We show here that risk-taking is a modifiable behavior that depends on right hemisphere prefrontal activity. We used low-frequency, repetitive transcranial magnetic stimulation to transiently disrupt left or right dorsolateral prefrontal cortex (DLPFC) function before applying a well known gambling paradigm that provides a measure of decision-making under risk. Individuals displayed significantly riskier decision-making after disruption of the right, but not the left, DLPFC. Our findings suggest that the right DLPFC plays a crucial role in the suppression of superficially seductive options. This confirms the asymmetric role of the prefrontal cortex in decision-making and reveals that this fundamental human capacity can be manipulated in normal subjects through cortical stimulation. The ability to modify risk-taking behavior may be translated into therapeutic interventions for disorders such as drug abuse or pathological gambling.

Adult↗

PubMed2003

A functional-anatomical model for lipreading.

Regional cerebral blood flow (rCBF) PET scans were used to study the physiological bases of lipreading, a natural skill of extracting language from mouth movements, which contributes to speech perception in everyday life. Viewing connected mouth movements that could not be lexically identified and that evoke perception of isolated speech sounds (nonlexical lipreading) was associated with bilateral activation of the auditory association cortex around Wernicke's area, of left dorsal premotor cortex, and left opercular-premotor division of the left inferior frontal gyrus (Broca's area). The supplementary motor area was active as well. These areas have all been implicated in phonological processing, speech and mouth motor planning, and execution. In addition, nonlexical lipreading also differentially activated visual motion areas. Lexical access through lipreading was associated with a similar pattern of activation and with additional foci in ventral- and dorsolateral prefrontal cortex bilaterally and in left inferior parietal cortex. Linear regression analysis of cerebral blood flow and proficiency for lexical lipreading further clarified the role of these areas in gaining access to language through lipreading. The results suggest cortical activation circuits for lipreading from action representations that may differentiate lexical access from nonlexical processes.

Adult↗

PubMed2001

Mapping adolescent brain change reveals dynamic wave of accelerated gray matter loss in very early-onset schizophrenia.

Neurodevelopmental models for the pathology of schizophrenia propose both polygenetic and environmental risks, as well as early (pre/perinatal) and late (usually adolescent) developmental brain abnormalities. With the use of brain mapping algorithms, we detected striking anatomical profiles of accelerated gray matter loss in very early-onset schizophrenia; surprisingly, deficits moved in a dynamic pattern, enveloping increasing amounts of cortex throughout adolescence. Early-onset patients were rescanned prospectively with MRI, at 2-year intervals at three time points, to uncover the dynamics and timing of disease progression during adolescence. The earliest deficits were found in parietal brain regions, supporting visuospatial and associative thinking, where adult deficits are known to be mediated by environmental (nongenetic) factors. Over 5 years, these deficits progressed anteriorly into temporal lobes, engulfing sensorimotor and dorsolateral prefrontal cortices, and frontal eye fields. These emerging patterns correlated with psychotic symptom severity and mirrored the neuromotor, auditory, visual search, and frontal executive impairments in the disease. In temporal regions, gray matter loss was completely absent early in the disease but became pervasive later. Only the latest changes included dorsolateral prefrontal cortex and superior temporal gyri, deficit regions found consistently in adult studies. These emerging dynamic patterns were (i) controlled for medication and IQ effects, (ii) replicated in independent groups of males and females, and (iii) charted in individuals and groups. The resulting mapping strategy reveals a shifting pattern of tissue loss in schizophrenia. Aspects of the anatomy and dynamics of disease are uncovered, in a changing profile that implicates genetic and nongenetic patterns of deficits.

Adolescent↗

PubMed2003

A specific deficit in context processing in the unaffected siblings of patients with schizophrenia.

BACKGROUND: Understanding the biological basis of complex, heritable illnesses such as schizophrenia is facilitated by sensitive and functionally specific measures of intermediate processes. Context processing is a theoretically motivated construct associated with executive function. Impairments in this process have been associated with dysfunction of the prefrontal cortex. In the present study, we evaluated whether a specific deficit in context processing could be associated with the unexpressed genetic liability to schizophrenia. METHODS: Twenty-four patients with schizophrenia, 24 unaffected siblings and 36 control subjects completed a version of the AX task with (1) a condition that required context processing and (2) an expectancy condition in which intact context processing could lead to errors. RESULTS: Patients and unaffected siblings performed relatively worse in the context processing condition, whereas controls performed relatively worse in the expectancy condition. A double dissociation between siblings and controls (F = 9.5, P<.005) constituted strong evidence of a specific deficit in context processing associated with a familial or genetic liability to schizophrenia. Preliminary evidence of high diagnostic efficiency was also noted (specificity, 38%; and sensitivity, 100%). CONCLUSIONS: Context processing deficits have been associated with dorsolateral prefrontal cortex dysfunctions in schizophrenia. Such a dysfunction may occur even when genetic liability to schizophrenia is unexpressed clinically. The present method of demonstrating a double dissociation may be a useful approach to exploring endophenotypes related to specific cognitive and neural processes that can be measured in ways sensitive to subtle group differences.

Adult↗

PubMed2002

Asymmetries of prefrontal cortex in human episodic memory: effects of transcranial magnetic stimulation on learning abstract patterns.

Functional neuroimaging suggests asymmetries of memory encoding and retrieval in the prefrontal lobes, but different hypotheses have been presented concerning the nature of prefrontal hemispheric specialization. We studied an associative memory task involving pairs of Kanji (Chinese) pictographs and unfamiliar abstract patterns. Subjects were ten Japanese adults fluent in Kanji, so only the abstract patterns represented novel material. During encoding, transcranial magnetic stimulation (TMS) was applied over the left and right dorsolateral prefrontal cortex (DLPFC). A significant (P<0.05) reduction in subsequent recall of new associations was seen only with TMS over the right DLPFC. This result suggests that the right DLPFC contributes to encoding of visual-object associations, and is consistent with a material-specific rather than a process-specific model of mnemonic function in DLPFC.

Adult↗

PubMed1988

Common cortical and subcortical targets of the dorsolateral prefrontal and posterior parietal cortices in the rhesus monkey: evidence for a distributed neural network subserving spatially guided behavior.

Common efferent projections of the dorsolateral prefrontal cortex and posterior parietal cortex were examined in 3 rhesus monkeys by placing injections of tritiated amino acids and HRP in frontal and parietal cortices, respectively, of the same hemisphere. Terminal labeling originating from both frontal and parietal injection sites was found to be in apposition in 15 ipsilateral cortical areas: the supplementary motor cortex, the dorsal premotor cortex, the ventral premotor cortex, the anterior arcuate cortex (including the frontal eye fields), the orbitofrontal cortex, the anterior and posterior cingulate cortices, the frontoparietal operculum, the insular cortex, the medial parietal cortex, the superior temporal cortex, the parahippocampal gyrus, the presubiculum, the caudomedial lobule, and the medial prestriate cortex. Convergent terminal labeling was observed in the contralateral hemisphere as well, most prominently in the principal sulcal cortex, the superior arcuate cortex, and the superior temporal cortex. In certain common target areas, as for example the cingulate cortices, frontal and parietal efferents terminate in an array of interdigitating columns, an arrangement much like that observed for callosal and associational projections to the principal sulcus (Goldman-Rakic and Schwartz, 1982). In other areas, frontal and parietal terminals exhibit a laminar complementarity: in the depths of the superior temporal sulcus, prefrontal terminals are densely distributed within laminae I, III, and V, whereas parietal terminals occupy mainly laminae IV and VI directly below the prefrontal bands. Subcortical structures also receive apposing or overlapping projections from both prefrontal and parietal cortices. The dorsolateral prefrontal and posterior parietal cortices project to adjacent, longitudinal domains of the neostriatum, as has been described previously (Selemon and Goldman-Rakic, 1985); these projections are also found in close apposition in the claustrum, the amygdala, the caudomedial lobule, and throughout the anterior medial, medial dorsal, lateral dorsal, and medial pulvinar nuclei of the thalamus. In the brain stem, both areas of association cortex project to the intermediate layers of the superior colliculus and to the midline reticular formation of the pons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1995

Increased sensitivity to the sensorimotor gating-disruptive effects of apomorphine after lesions of medial prefrontal cortex or ventral hippocampus in adult rats.

Sensorimotor gating of the startle reflex is impaired in humans with schizophrenia and in rats after mesolimbic D2 dopamine receptor activation. The loss of startle gating after D2 activation in rats has been used as an animal model of impaired sensorimotor gating in schizophrenia, because the ability of antipsychotics to restore startle gating in D2-activated rats correlates significantly with antipsychotic clinical potency. Substantial evidence indicates that the pathophysiology of schizophrenia includes structural and functional deficits in prefrontal and temporal regions, particularly the dorsolateral prefrontal cortex and the hippocampus and parahippocampal gyrus. The present study assessed startle gating in adult rats after ibotenic acid lesions of the medial prefrontal cortex or ventral hippocampus. Medial prefrontal cortex lesioned rats exhibited normal startle amplitude and normal sensorimotor gating, as reflected by prepulse inhibition (PPI) of the startle reflex. Hippocampus lesioned rats exhibited elevated startle amplitude, and similar to rats with medial prefrontal cortex lesions, did not show significant changes in basal PPI. Low doses of the mixed dopamine agonist apomorphine did not significantly reduce PPI in sham lesioned rats, but significantly disrupted PPI in both medial prefrontal cortex- and ventral hippo-campus lesioned rats. These data are consistent with the hypothesis that cell damage in frontal and temporal cortex increases the sensitivity to the sensorimotor gating-disruptive effects of dopamine receptor activation.

Animals↗

PubMed1988

Androgen binding and metabolism in the cerebral cortex of the developing rhesus monkey.

The influence of gonadal steroids on the maturation of the cerebral cortex and their possible influence on cortical function are not well understood. The present study examines androgen binding and metabolism in regions of the cerebral cortex and several subcortical structures at different time points during the development of the rhesus monkey. Androgen binding and metabolism were assessed in selected cortical and subcortical regions from neonatal, juvenile, and adult rhesus monkeys. Specific high affinity androgen-binding sites (apparent equilibrium dissociation constants for [3H]R1881, 0.04-0.3 nM) were observed in many areas of the rhesus monkey brain. These areas included (but were not limited to) the hypothalamus, amygdala, dorsolateral prefrontal cortex, orbital prefrontal cortex, visual and somatosensory cortex, and corpus callosum. Although the highest level of androgen binding was observed in the hypothalamus (8-20 fmol/mg protein), cortical samples also had measurable levels of binding (1-5 fmol/mg protein). No apparent regional or developmental differences in the number or affinity of androgen-binding sites were detected in animals ranging from 1 week to 8 yr in age. Androgen metabolism via aromatization and 5 alpha-reduction was observed in all regions of the neocortex examined, although at lower levels than in the hypothalamus and amygdala. Overall production of estrogens and 5 alpha-reduced androgens declined approximately 10-fold from prenatal to early postnatal life in both cortical and subcortical structures. The presence of androgen binding and metabolism in the monkey cerebral cortex indicates that steroid hormones may have considerable impact on cortical function in primates at postnatal as well as prenatal ages.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1997

Prefrontal cortex cognitive deficits in children treated early and continuously for PKU.

To begin to study the importance of dopamine for executive function abilities dependent on prefrontal cortex during early childhood, the present investigation studied children in whom we predicted reduced dopamine in prefrontal cortex but otherwise normal brains. These are children treated early and continuously for the metabolic disorder phenylketonuria (PKU). Untreated PKU is the most common biochemical cause of mental retardation. The root problem is an inability to convert one amino acid, phenylalanine (Phe), into another, tyrosine (Tyr), the precursor of dopamine. Phe levels in the bloodstream soar; Tyr levels fall. Treatment with a diet low in Phe reduces the Phe:Tyr imbalance but cannot eliminate it. We hypothesized that the resultant modest elevation in the ratio of Phe to Tyr in the blood, which results in slightly less Tyr reaching the brain, uniquely affects the cognitive functions dependent on prefrontal cortex because of the special sensitivity of prefrontally projecting dopamine neurons to small decreases in Tyr. In a 4-year longitudinal study, we found that PKU children whose plasma Phe levels were three to five times normal (6-10 mg/dl) performed worse than other PKU children with lower Phe levels, matched controls, their own siblings, and children from the general population on tasks that required the working memory and inhibitory control abilities dependent on dorsolateral prefrontal cortex. The impairment was as evident in our oldest age range (3 1/2-7 years) as it was in the youngest (6-12 months). The higher a child's Phe level, the worse that child's performance. Girls were more adversely affected than boys. The deficit appears to be selective, affecting principally one neural system, since even PKU children with Phe levels three to five times normal performed well on the 13 control tasks. Clinical implications for the treatment of PKU and other neurodevelopmental disorders are discussed.

Age Factors↗

PubMed2001

Activation of prefrontal cortex and anterior thalamus in alcoholic subjects on exposure to alcohol-specific cues.

BACKGROUND: Functional imaging studies have recently demonstrated that specific brain regions become active in cocaine addicts when they are exposed to cocaine stimuli. To test whether there are regional brain activity differences during alcohol cue exposure between alcoholic subjects and social drinkers, we designed a functional magnetic resonance imaging (fMRI) protocol involving alcohol-specific cues. METHODS: Ten non-treatment-seeking adult alcoholic subjects (2 women) (mean [SD] age, 29.9 [9.9] years) as well as 10 healthy social drinking controls of similar age (2 women) (mean [SD] age, 29.4 [8.9] years) were recruited, screened, and scanned. In the 1.5-T magnetic resonance imaging scanner, subjects were serially rated for alcohol craving before and after a sip of alcohol, and after a 9-minute randomized presentation of pictures of alcoholic beverages, control nonalcoholic beverages, and 2 different visual control tasks. During picture presentation, changes in regional brain activity were measured with the blood oxygen level-dependent technique. RESULTS: Alcoholic subjects, compared with the social drinking subjects, reported higher overall craving ratings for alcohol. After a sip of alcohol, while viewing alcohol cues compared with viewing other beverage cues, only the alcoholic subjects had increased activity in the left dorsolateral prefrontal cortex and the anterior thalamus. The social drinkers exhibited specific activation only while viewing the control beverage pictures. CONCLUSIONS: When exposed to alcohol cues, alcoholic subjects have increased brain activity in the prefrontal cortex and anterior thalamus-brain regions associated with emotion regulation, attention, and appetitive behavior.

Alcohol Drinking↗

PubMed2004

Neural mechanisms of Korean word reading: a functional magnetic resonance imaging study.

The use of functional magnetic resonance imaging permits the collection of brain activation patterns when native Korean speakers (12 persons as subjects) read Korean words and Chinese characters. The Korean language uses both alphabetic Korean words and logographic Chinese characters in its writing system. Our experimental results show that the activation patterns obtained for reading Chinese characters by Korean native speakers involve neural mechanisms that are similar to Chinese native speakers; i.e. strong left-lateralized middle frontal cortex activation. For the case of Korean word reading, the activation pattern in the bilateral fusiform gyrus, left middle frontal gyrus, left superior temporal gyrus, right mid temporal gyrus, precentral gyrus, and insula was observed. This suggests that the activation pattern for Korean word reading appears to corroborate with that of alphabetic words at the general level. A further noteworthy finding of our study is the strong activation of the posterior part of the right dorsolateral prefrontal cortex (BA 8). The right hemispheric BA 8 belongs to the visual higher order control area and we propose that this area should be responsible for processing of visuospatial (surface form) information of Korean words.

Adult↗

PubMed1984

Caudate unit activity during operant feeding behavior in monkeys and modulation by cooling prefrontal cortex.

Activity was recorded from 351 neurons in the head of the caudate nucleus (CD) of monkeys during an operant feeding task consisting of: (1) food or non-food presentation (P); (2) bar pressing (B); and (3) food acquisition and ingestion (I). Of 45 neurons which responded in the P phase and were tested systematically, 27 responded to visual presentation of both food and non-food (non-specific response), and 18 responded to food presentation only (food specific response). The magnitude of food specific responses depended on the nature of the food and was inversely related to the latency of the onset of bar pressing. Thirty-five neurons responded in the B phase: 28 changed firing rate continuously with no correlation to individual bar presses, while the activity of the other 7 was related to each bar press. In the I phase, 62 neurons responded to separate events: the activity of more than half (39 neurons) was often related to chewing movement or gustatory stimuli, and that of one third (23 neurons) changed during individual arm movements. The neurons which responded in the P phase were found to be distributed widely in the head of the CD except for its central zone, while the neurons which responded in the I phase were in the medial part. Cooling of the dorsolateral prefrontal cortex abolished the continuous responses seen in the B phase, but did not abolish the feeding behavior. The data suggest that in the head of the CD there are several groups of neurons that have different functions and different distributions: food specific, sensory integration responses, non-motor responses driven by the frontal cortex, motor responses coupled to various movements, and sensory responses which apparently originate in the intra-oral cavity. These functions may arise sequentially, or in correspondence with integration of the sensory and motor systems to produce coordinated behavior.

Animals↗