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B Blum

Publications and source records attributed to B Blum.

107 records · Page 6Linked to original sources
PubMedDate not supplied

Manipulation reach and visual reach neurons in the inferior parietal lobule of the rhesus monkey.

The characteristics of inferior parietal lobule (IPL) 'reach cell' responses were studied in the fixating monkey in order to obtain a clue to the function of this area in manipulative behavior. Two subclasses of reach neurons, one showing visual receptive field sensitivity, the other lacking such responsiveness are proposed as correlates of two types of reach behavior, one that takes place with, the other without visual guidance, respectively. Neuronal firing increment and/or firing decrement responses, stimulus-bound to reach behavior were obtained from either type of cell. These were presented as equivalent modes of signal encoding, on the basis of the transformability of neuronal firing increment to firing decrement response as a result of preconditioning stimulation of the oral pulvinar nucleus. Many of the responses obtained were bimodal and some were biphasic, i.e. consisting of incremental and decremental firing phases. As each such component was independently modifiable, they were regarded different signal entities. The multicomponental nature of the visual reach neuronal response was manifested when the reaching movement was into the receptive field of the neuron. Responses consisted then of an initial component, presumably visual, prefixed to a response component stimulus-bound to the reach-invoking stimuli. The early component occupied the same position as the visual response of the cell obtained with visual receptive field stimulation alone. Moreover, the early component could be negated by preconditioning stimulation of the LP and/or pulvinar targets, and then the residual response simulated the response of a non-visual reach neuron.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

A head holder and stereotaxic device for the rattlesnake.

We describe an apparatus for immobilization of the rattlesnake head for brain experimentation. Its design also allows its use as a stereotaxic instrument for electrophysiological studies employing microelectrodes. Attachment of the head is at the two orbital ridges and the hard palate. The bregma provides a zero reference for the frontal, lateral, and depth coordinates.

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PubMedDate not supplied

The functional relationship of monkey infra parietal cortex (IPL) to behavior in the extrapersonal space.

Lesions of the posterior parietal system in humans and of the presumably homologous area 7 of the monkey cause impairment in high-order manipulative behavior. A specific "misreaching" observed prompted the outlook of dysfunction constrained to the perceptual, the comand/motor aspects excluded. To clarify the nature of normal functioning in this domain, a study was done by microelectrode recording from area 7 of the monkey of neural firing in relation to hand reaching to targets. The data obtained show that an area 7 neuron fires in relation to simple stimuli, such as a square of white light, and to composite stimuli, such as hand reaching by the monkey or by the trainer in the monkey's extrapersonal space, the response to complex stimuli characteristically multiduty. The firing patterns were presumably relatable to encoding of stimulus components with superposed situation variance. Selectivity of the stimulus was maintained along specific invariance, such as to hand used, to direction of outgoing reaching, to direction from which the rewarding hand of the trainer reached. It is proposed that functional linkage of cognate features, a consequent modular category encoding and "packaging" of information relevant for praxis schema, is thus achieved by area 7 cells specialized for integrating information in the time and space domains visual, tactile, proprioceptive/kinaesthetic, and other for the sake of behavior in extrapersonal space. Generalization without jeopardizing of differentiating is presumably enabled through the multiduty cell entity.

Animals↗
PubMedDate not supplied

Coherence in localized visual evoked potentials (VEPs) to spatial stimulus attributes (orientation and displacement) in man.

The purpose of this study was to compare visual evoked potentials (VEPs) of striate-peristriate and Cz to posterior parietal, especially IPL's supramarginal (Su) and angular (Ang, Ano, and Ant) leads in response to human face spatial attributes attend-task, to assess the concern of the former with basic features versus the latter's spatial attributes "rotated" rightwards, leftwards, or oblique (unusual angle of sight) or nodal one (eye)- and two-item, eye/mouth displacement. Monopolar cranially derived VEPs were recorded bihemispherically from six adults using 12 electrode arrays 1.5 to 2 cm apart. Subjects were instructed to fixate a marking on the monitor at a nodal eyebrow region, while attending the stimulus that was computer displayed for 200 or 300 ms, and followed by mask. Analysis was made on the first 240 ms of the records after stimulus onset; the test was compared to "full face," the hypothesized control. Localized VEP changes were observed task-bound and bihemispherically coherent in parietal leads, especially Ang, Ano, and Su. The early negativity of the "full face" control was replaced by an early positive wave with onset latencies of 70 +/- 15 ms, significantly shorter (p < 0.01) than the striate's 90 +/- 20 ms. The changes were observed for both rotation and displacement. The changes in the angular leads (Ano and Ang) are consistent with the encoding of spatial attributes of orientation and nodal face items displacement. Differentiation of direction and degree of rotation, "seen from above" versus "seen from below," largely encoded by the right Su. The composite double-item eye and displaced or obliquely rotated induced extended coherent activity in parietal leads. Oz, peristriate, and Cz showed no such changes. No attempt is made to imply source localization; we claim parietal localized and coherency of the VEP changes suggest high-order early processing of human face attributes. This occurs by a relatively fast pathway. The "triggers" for the changes are direction and degree of rotation or of displacement rather than actual geometry of the stimulus.

Adult↗