Subdivisions of inferior temporal cortex in squirrel monkeys make dissociable contributions to visual learning and memory.

The malleability of object representations by experience is essential for adaptive behavior. It has been hypothesized that neurons in inferior temporal cortex (IT) in monkeys are pivotal in visual association learning, evidenced by experiments revealing changes in neural selectivity following visual learning, as well as by lesion studies, wherein functional inactivation of IT impairs learning. A critical question remaining to be answered is whether IT neuronal activity is sufficient for learning. To address this question directly, we conducted experiments combining visual classification learning with microstimulation in IT. We assessed the effects of IT microstimulation during learning in cases where the stimulation was exclusively informative, conditionally informative, and informative but not necessary for the classification task. The results show that localized microstimulation in IT can be used to establish visual classification learning, and the same stimulation applied during learning can predictably bias judgments on subsequent recognition. The effect of induced activity can be explained neither by direct stimulation-motor association nor by simple detection of cortical stimulation. We also found that the learning effects are specific to IT stimulation as they are not observed by microstimulation in an adjacent auditory area. Our results add the evidence that the differential activity in IT during visual association learning is sufficient for establishing new associations. The results suggest that experimentally manipulated activity patterns within IT can be effectively combined with ongoing visually induced activity during the formation of new associations.

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rTMS Induces Brain Functional and Structural Alternations in Schizophrenia Patient With Auditory Verbal Hallucination

Frontiers in Neuroscience ◽

10.3389/fnins.2021.722894 ◽

2021 ◽

Vol 15 ◽

Author(s):

Yuanjun Xie ◽

Muzhen Guan ◽

Zhongheng Wang ◽

Zhujing Ma ◽

Huaning Wang ◽

...

Keyword(s):

Clinical Symptoms ◽

Psychiatric Symptoms ◽

Visual Learning ◽

Verbal Learning ◽

Temporal Cortex ◽

Low Frequency ◽

Inferior Temporal Cortex ◽

Positive Symptoms ◽

Neural Basis ◽

Auditory Verbal Hallucination

BackgroundLow-frequency transcranial magnetic stimulation (rTMS) over the left temporoparietal cortex reduces the auditory verbal hallucination (AVH) in schizophrenia. However, the underlying neural basis of the rTMS treatment effect for schizophrenia remains not well understood. This study investigates the rTMS induced brain functional and structural alternations and their associations with clinical as well as neurocognitive profiles in schizophrenia patients with AVH.MethodsThirty schizophrenia patients with AVH and thirty-three matched healthy controls were enrolled. The patients were administered by 15 days of 1 Hz rTMS delivering to the left temporoparietal junction (TPJ) area. Clinical symptoms and neurocognitive measurements were assessed at pre- and post-rTMS treatment. The functional (amplitude of low-frequency fluctuation, ALFF) and structural (gray matter volume, GMV) alternations were compared, and they were then used to related to the clinical and neurocognitive measurements after rTMS treatment.ResultsThe results showed that the positive symptoms, including AVH, were relieved, and certain neurocognitive measurements, including visual learning (VisLearn) and verbal learning (VerbLearn), were improved after the rTMS treatment in the patient group. Furthermore, the rTMS treatment induced brain functional and structural alternations in patients, such as enhanced ALFF in the left superior frontal gyrus and larger GMV in the right inferior temporal cortex. The baseline ALFF and GMV values in certain brain areas (e.g., the inferior parietal lobule and superior temporal gyrus) could be associated with the clinical symptoms (e.g., positive symptoms) and neurocognitive performances (e.g., VerbLearn and VisLearn) after rTMS treatment in patients.ConclusionThe low-frequency rTMS over the left TPJ area is an efficacious treatment for schizophrenia patients with AVH and could selectively modulate the neural basis underlying psychiatric symptoms and neurocognitive domains in schizophrenia.

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Qualitative and quantitative features of axons projecting from caudal to rostral inferior temporal cortex of squirrel monkeys

Visual Neuroscience ◽

10.1017/s0952523800008981 ◽

1995 ◽

Vol 12 (4) ◽

pp. 701-722 ◽

Cited By ~ 8

Author(s):

G.E. Steele ◽

R.E. Weller

Keyword(s):

Visual Information ◽

Temporal Cortex ◽

Squirrel Monkeys ◽

Inferior Temporal Cortex ◽

Type I ◽

Type Ii ◽

Areal Extent ◽

Type Iii ◽

Terminal Arbor ◽

Mean Width

AbstractOn the basis of cortical and subcortical connections and architectonics, inferior temporal (IT) cortex of squirrel monkeys consists of a caudal region, ITC, with dorsal (ITCd) and ventral (ITCv) subdivisions; a rostral region, ITR; and possibly a third region intermediate to ITC and ITR, IT1 (Weller & Steele, 1992; Steele & Weller, 1993). The present study qualitatively and quantitatively examined the terminal arborizations of 26 axons in ITR and IT1 labeled by injections of biocytin or, in one case, horseradish peroxidase, in ITCv. The majority of axons gave rise to a single terminal arbor, with a small number branching into two overlapping or nearby arbors. Presumptive terminal specializations consisted of rounded, bead-like swellings, most often located en passant. All axons terminated in layer 4 of cortex, and most had additional terminations in layers 3 and 5. The total extent of each axon's terminal arbor was 125–750 μm dorsoventrally (mean = 360.6 μm) and 150–725 μm anteroposteriorly (mean = 328.1 μm; all values uncorrected for shrinkage). In most axons, especially those with larger terminal fields, boutons were not uniformly distributed, but formed 2–4 clumps (mean = 2.2), with a mean width of 149 μm, separated by narrower regions of fewer boutons. Based on a cluster analysis of characteristics of the 26 axons, axons projecting from caudal (ITCv) to rostral (ITR or IT1) IT cortex of squirrel monkeys comprised three groups that we called Type I, Type II, and Type III. Type I axons, the smallest in areal extent of terminal arbor, terminated predominantly in dorsal ITR. Type III axons, largest in areal extent, and Type II axons, intermediate in areal extent, terminated in ventral ITR and throughout IT1. The three classes of axons may correspond to different types of visual information entering rostral IT cortex. The clumping of boutons suggests that individual axons terminate in limited patches within their terminal fields.

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Cortical connections of subdivisions of inferior temporal cortex in squirrel monkeys

The Journal of Comparative Neurology ◽

10.1002/cne.903240105 ◽

1992 ◽

Vol 324 (1) ◽

pp. 37-66 ◽

Cited By ~ 27

Author(s):

R. E. Weller ◽

G. E. Steele

Keyword(s):

Temporal Cortex ◽

Squirrel Monkeys ◽

Inferior Temporal Cortex ◽

Cortical Connections

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Subcortical connections of subdivisions of inferior temporal cortex in squirrel monkeys

Visual Neuroscience ◽

10.1017/s0952523800004776 ◽

1993 ◽

Vol 10 (3) ◽

pp. 563-583 ◽

Cited By ~ 39

Author(s):

G. E. Steele ◽

R. E. Weller

Keyword(s):

Temporal Cortex ◽

Squirrel Monkeys ◽

Inferior Temporal Cortex ◽

Reticular Nucleus ◽

Subcortical Structures ◽

Basal Nucleus ◽

Basal Nuclei ◽

Medial Nucleus ◽

Rostral Region ◽

Area Te

AbstractOn the basis of cortical connections and architectonics, inferior temporal (IT) cortex of squirrel monkeys consists of a caudal, prestriate-recipient region, ITC; a rostral region, ITR; and possibly an intermediate region along the border of ITC and ITR, ITI (Weller & Steele, 1992). ITC contains dorsal (ITCd) and ventral (ITCv) areas. The subcortical connections of these subdivisions of IT cortex were determined in the present study from the results of cortical injections of wheat-germ agglutinin conjugated to horseradish peroxidase, [3H]-amino acids and fast blue. ITC and ITR receive afferents from the locus coeruleus, dorsal raphe, nucleus annularis, central superior nucleus, pontine reticular formation, lateral hypothalamus, paracentral nucleus, and central medial nucleus; send efferents to the superior colliculus, reticular nucleus, and striatum; and have both afferent and efferent connections with the pretectum, pulvinar, claustrum, amygdala, and basal nucleus of Meynert. ITC and ITR have different patterns of connections with a number of subcortical structures, including the pulvinar and amygdala. Injections in ITC strongly label multiple nuclei of the inferior pulvinar and the medial division of the lateral pulvinar (PLM), and moderately label the medial pulvinar (PM), whereas injections in ITR strongly label PM and moderately label PLM. Injections in ITC label sparse projections to the lateral nucleus of the amygdala, in contrast to injections in ITR that label strong projections to the lateral and basal nuclei of the amygdala. Injections in “IT” produce a pattern of subcortical label that has some features of that observed from injections in ITC and that observed from injections in ITR. Although most of the connections of ITCd and ITCv appear similar, only injections involving ITCd label the middle nucleus of the inferior pulvinar (PIM).Comparison of the subcortical connections of subdivisions of IT cortex in squirrel monkeys and what is presently known of the subcortical connections of subdivisions of IT cortex in macaque monkeys supports the previous suggestion that ITC of squirrel monkeys may be comparable to area TEO of macaques, IT, may be comparable to posterior area TE, and ITR may be comparable to anterior area TE (Weller & Steele, 1992).

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