TY  - JOUR
AU  - Mehta, AD
AU  - Ulbert, István
AU  - Schroeder, CE
TI  - Intermodal selective attention in monkeys. I: distribution and timing of effects across visual areas.
JF  - CEREBRAL CORTEX
J2  - CEREB CORTEX
VL  - 10
PY  - 2000
IS  - 4
SP  - 343
EP  - 358
PG  - 16
SN  - 1047-3211
UR  - https://m2.mtmt.hu/api/publication/1121137
ID  - 1121137
AB  - This study quantified the magnitude and timing of selective attention effects
across areas of the macaque visual system, including the lateral geniculate
nucleus (LGN), lower cortical areas V1 and V2, and multiple higher visual areas
in the dorsal and ventral processing streams. We used one stimulus configuration 
and behavioral paradigm, with simultaneous recordings from different areas to
allow direct comparison of the distribution and timing of attention effects
across the system. Streams of interdigitated auditory and visual stimuli were
presented at a high rate with an irregular interstimulus interval (mean of 4/s). 
Attention to visual stimuli was manipulated by requiring subjects to make
discriminative behavioral responses to stimuli in one sensory modality, ignoring 
all stimuli in the other. The attended modality was alternated across trial
blocks, and difficulty of discrimination was equated across modalities. Stimulus 
presentation was gated, so that no stimuli were presented unless the subject
gazed at the center of the visual stimulus display. Visual stimuli were diffuse
light flashes differing in intensity or color and subtending 12 degrees centered 
at the point of gaze. Laminar event-related potential (ERP) and current source
density (CSD) response profiles were sampled during multiple paired penetrations 
in multiple visual areas with linear array multicontact electrodes. Attention
effects were assessed by comparing responses to specific visual stimuli when
attended versus when visual stimuli were looked at the same way, but ignored.
Effects were quantified by computing a modulation index (MI), a ratio of the
differential CSD response produced by attention to the sum responses to attended 
and ignored visual stimuli. The average MI increased up levels of the lower
visual pathways from none in the LGN to 0.0278 in V1 to 0.101 in V2 to 0.170 in
V4. Above the V2 level, attention effects were larger in ventral stream areas (MI
= 0. 152) than in dorsal stream areas (MI = 0.052). Although onset latencies were
shortest in dorsal stream areas, attentional modulation of the early response was
small relative to the stimulus-evoked response. Higher ventral stream areas
showed substantial attention effects at the earliest poststimulus time points,
followed by the lower visual areas V2 and V1. In all areas, attentional
modulation lagged the onset of the stimulus-evoked response, and attention
effects grew over the time course of the neuronal response. The most powerful,
consistent, and earliest attention effects were those found to occur in area V4, 
during the 100-300 ms poststimulus interval. Smaller effects occurred in V2 over 
the same interval, and the bulk of attention effects in V1 were later. In the
accompanying paper, we describe the physiology of attention effects in V1, V2 and
V4.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Kovács, Ilona
AU  - T V, Papathomas
AU  - M, Yang
AU  - Á, Fehér
TI  - When the brain changes its mind: Interocular grouping during binocular rivalry
JF  - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
J2  - P NATL ACAD SCI USA
VL  - 93
PY  - 1996
SP  - 15508
EP  - 15510
PG  - 3
SN  - 0027-8424
DO  - 10.1073/pnas.93.26.15508
UR  - https://m2.mtmt.hu/api/publication/2627507
ID  - 2627507
AB  - The prevalent view of binocular rivalry holds that it is a competition between the two eyes mediated by reciprocal inhibition among monocular neurons. This view is largely due to the nature of conventional rivalry-inducing stimuli, which are pairs of dissimilar images with coherent patterns within each eye's image. Is it the eye of origin or the coherency of patterns that determines perceptual alternations between coherent percepts in binocular rivalry? We break the coherency of conventional stimuli and replace them by complementary patchworks of intermingled rivalrous images. Can the brain unscramble the pieces of the patchwork arriving from different eyes to obtain coherent percepts? We find that pattern coherency in itself can drive perceptual alternations, and the patchworks are reassembled into coherent forms by most observers. This result is in agreement with recent neurophysiological and psychophysical evidence demonstrating that there is more to binocular rivalry than mere eye competition.
LA  - English
DB  - MTMT
ER  -