Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Dynamics of directional selectivity in MT receptive field centre and surround
    Perge, János A. ; Borghuis, Bart G. ; Bours, Roger J.E. ; Lankheet, Martin J.M. ; Wezel, Richard J.A. Van - \ 2005
    European Journal of Neuroscience 22 (2005)8. - ISSN 0953-816X - p. 2049 - 2058.
    Electrophysiology - Extrastriate cortex - Macaque monkey - Middle temporal area - Motion perception

    We studied receptive field organization of motion-sensitive neurons in macaque middle temporal cortical area (MT), by mapping direction selectivity in space and in time. Stimuli consisted of pseudorandom sequences of single motion steps presented simultaneously at many different receptive field locations. Spatio-temporal receptive field profiles were constructed by cross-correlating stimuli and spikes. The resulting spike-triggered averages revealed centre-surround organization. The temporal dynamics of the receptive fields were generally biphasic with increased probability for the preferred direction at short latency (50-70 ms) and decreased probability at longer latency (80-100 ms). The response latency of the receptive field surround was on average 16 ms longer than that of the centre. Our results show that surround input and biphasic behaviour reflect two different mechanisms, which make MT cells specifically sensitive to motion contrast in space and time.

    Temporal-chromatic interactions in LGN P-cells
    Lankheet, Martin J.M. ; Lennie, Peter ; Krauskopf, John - \ 1998
    Visual Neuroscience 15 (1998)1. - ISSN 0952-5238 - p. 47 - 54.
    Chromatic properties - Lateral geniculate nucleus (LGN) - Macaque monkey - P-cells - Temporal properties

    We studied the interaction between the chromatic and temporal properties of parvocellular (P) neurons in the lateral geniculate nucleus (LGN) of macaque monkeys. We measured the amplitudes and phases of responses to stimulation by spatially uniform fields modulated sinusoidally about a white point in a three-dimensional color space, at a range of temporal frequencies between 1 and 25 Hz. Below about 4 Hz, temporal frequency had relatively little effect on chromatic tuning. At higher frequencies chromatic opponency was weakened in almost all cells. The complex interactions between temporal and chromatic properties are represented by a linear filter model that describes response amplitude and phase as a function of temporal frequency and direction in color space along which stimuli are modulated. The model stipulates the cone inputs to center and surround, their temporal properties, and the linear combination of center and surround signals. It predicts the amplitudes and phases of responses of P-cells, and the change of chromatic properties with temporal frequency. We used the model to investigate whether or not the chromatic signature of the surround in a red-green cell could be estimated from the change in the cell's chromatic properties with temporal frequency. Our findings could be equally well described by mixed cone surrounds as by pure cone surrounds, and we conclude that, with regard to temporal properties, there is no benefit to be gained by segregating cone classes in center and surround.

    Distinctive characteristics of subclasses of red-green P-cells in LGN of macaque
    Lankheet, Martin J.M. ; Lennie, Peter ; Krauskopf, John - \ 1998
    Visual Neuroscience 15 (1998)1. - ISSN 0952-5238 - p. 37 - 46.
    Chromatic properties - Lateral geniculate nucleus (LGN) - Macaque monkey - P-cells - Temporal properties

    We characterized the chromatic and temporal properties of a sample of 177 red-green parvocellular neurons in the LGN of Macaco, nemestrina using large-field stimuli modulated along different directions through a white point in color space. We examined differences among the properties of the four subclasses of red-green P-cells (on- and off-center, red and green center). The responses of off-center cells lag the stimulus more than do those of on-center cells. At low temporal frequencies, this causes the phase difference between responses of the two kinds of cells to be considerably less than 180 cleg. For isoluminant modulations the phases of on- and off-responses were more nearly 180 deg apart. A cell's temporal characteristics did not depend on the class of cone driving its center. Red center and green center cells have characteristically different chromatic properties, expressed either as preferred elevations in color space, or as weights with which cells combine inputs from L- and M-cones. Red center cells are relatively more responsive to achromatic modulation, and attach relatively more weight to input from the cones driving the center Off-center cells also attach relatively more weight than do on-center cells to input from the class of cone driving the center.

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