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  • 1
    ISSN: 1432-1106
    Keywords: Postcentral gyrus ; Area 1 ; Finger representation ; Neural integration ; Monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The representation of the hand and fingers in area 1 of the first somatosensory cortex was studied in conscious monkeys by recording single neuronal activity. The results are as follows. (1) We found multi-finger type receptive fields which cover more than one finger discontinuously or wide-field type ones which cover both finger and palmar skin or two halves of the palmar skin together. Multi-finger type receptive fields were also found in some joint manipulation neurons. Multifinger or wide-field type receptive fields were found in nearly 40% of area 1 neurons. The rate was even higher, up to 70%, in the medial part of the cortical finger region. Consequently, the finger representation in area 1 was less discretely somatotopic than that in area 3b. (2) The submodality content of area 1 was almost identical to that of area 3b: 74.5% and 20.9% of identified neurons were, respectively, cutaneous and deep. The distribution of neurons with different submodalities overlapped in area 1. (3) Among area 1 neurons with multi-finger type receptive fields, response characteristics of those with inhibitory receptive fields, those with directional selectivity to moving stimuli, and those with converging afferent inputs, were studied in detail. Evidence is presented to suggest that information from different parts of the body, or from the same body parts but different afferent sources, is integrated in area 1. (4) It is proposed that, within the SI, area 1 is the initial stage of integration of sensory information coming from the thalamus and from area 3a or 3b via cortico-cortical connections.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Monkey ; Postcentral gyrus ; Finger representation ; Vertical neuronal arrays ; Converging inputs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single neuronal activity was recorded in the crown of the postcentral gyrus (areas 1 and 2) in 5 conscious monkeys. A total of 93 penetrations were made in the hand and finger region of 9 hemispheres and 827 neurons were isolated. The receptive field characteristics of neurons recorded along each of 88 penetrations which entered perpendicularly to the cortical surface were compared. The majority of neurons in this region were responsive to skin stimulation. In 54 penetrations, neurons related to different sensory submodalities were mixed. In 30, skin neurons predominated, and in 8, ‘deep’ neurons, while in the remaining 16 penetrations neurons related to different submodalities were equally mixed. In 16 penetrations, neurons responded exclusively to stimulation of skin, hair or nails. In 9 penetrations, neurons were exclusively related to joint manipulation or other types of ‘deep’ submodality. In 9 penetrations, unidentified neurons were in the majority. In each penetration, the receptive field positions varied considerably on the same finger or encompassed more than one finger. Although neurons of the same submodality, either skin or ‘deep’ tended to be set in an array, the most adequate stimulus could vary among neurons of a given array. The variability in the receptive field positions or the most adequate stimuli remained constant irrespective of the angle of the electrode penetration in the cortex. The results are compatible with the idea that vertically arranged neuronal array receive inputs of multiple sources, both thalamacortical and corticocortical, so that interactions between different inputs can readilly occur.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Monkey ; Postcentral gyrus ; Vertical neuronal arrays ; Functional surfaces ; Active touch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single neuronal activity was recorded in the crown of the postcentral gyrus (areas 1 and 2) in 5 conscious monkeys. A total of 88 penetrations entered perpendicularly to the cortical surface. Among them, 6 examples are chosen and the receptive field characteristics of constituent neurons were described in some detail. Receptive fields of neurons recorded along a particular penetration were variable in their positions, but the largest receptive field usually covered the others. Neurons with the largest receptive fields were found most frequently in the infragranular layers. Often they included inhibitory receptive fields. The inhibitory receptive fields were arranged side-by-side to the excitatory ones, rather than in a center-surround fashion. The key stimulus common to neurons in a vertical penetration was the contact of an object to the receptive field achieved during animal's active behavior to manipulate the object. We thus designated the largest receptive field as a functional surface. Our results demonstrate that a vertical array of neurons in this cortical region can be regarded as a functional assemblage which deals with a set of information concerning one of various aspects of active touch.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Postcentral gyrus ; Area 3b ; Finger representation ; Functional subdivisions ; Monkeys
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The representation of fingers in the first somatosensory cortex was studied in conscious monkeys by recording single neuronal activity, and the following results were obtained: (1) In area 3a, most neurons responded to joint manipulation or other types of deep stimuli. The representation of five fingers was somatotopically arranged. (2) In area 3b, 77.7% and 20.9% of identified neurons responded to cutaneous and deep stimuli respectively. (3) Neurons responding to light mechanical stimuli and with receptive fields on the distal finger segment were found in the most anterior part of area 3b while those responding better to specific mechanical stimuli, such as rubbing, scraping, pinching, tapping, etc. of finger glabrous skin, were found in the more posterior part. The representation of the five fingers was somatotopically arranged. (4) Neurons responding to light or specific mechanical stimulation of the dorsal hairy skin of fingers were found in the posterior part of area 3b. The independent somatotopic representation of four fingers was recognized within this region. (5) Neurons responding to mechanical stimulation of the palmar skin were found in two separate regions, the medial one for the ulnar half and the lateral one for the radial half of the palm. (6) These results indicate that the representation of fingers in areas 3a and 3b of the conscious monkey is divided into multiple somatotopic subdivisions each representing a functional region of the hand and fingers. (7) Neurons with multi-finger receptive fields were occasionally found in area 3b, mostly in layer VI. Some of them had inhibitory receptive fields. Multifinger type receptive fields were more commonly found in area 1.
    Type of Medium: Electronic Resource
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