TY  - JOUR
AU  - Lakatos, Péter
AU  - Karmos, György
AU  - Mehta, AD
AU  - Ulbert, István
AU  - Schroeder, CE
TI  - Entrainment of neuronal oscillations as a mechanism of attentional selection.
JF  - SCIENCE
J2  - SCIENCE
VL  - 320
PY  - 2008
IS  - 5872
SP  - 110
EP  - 113
PG  - 4
SN  - 0036-8075
DO  - 10.1126/science.1154735
UR  - https://m2.mtmt.hu/api/publication/1121165
ID  - 1121165
N1  - Funding Agency and Grant Number: NIMH NIH HHS [MH060358] Funding Source: Medline; NATIONAL INSTITUTE OF MENTAL HEALTH [R01MH060358] Funding Source: NIH RePORTER
AB  - Whereas gamma-band neuronal oscillations clearly appear integral to visual
attention, the role of lower-frequency oscillations is still being debated.
Mounting evidence indicates that a key functional property of these oscillations 
is the rhythmic shifting of excitability in local neuronal ensembles. Here, we
show that when attended stimuli are in a rhythmic stream, delta-band oscillations
in the primary visual cortex entrain to the rhythm of the stream, resulting in
increased response gain for task-relevant events and decreased reaction times.
Because of hierarchical cross-frequency coupling, delta phase also determines
momentary power in higher-frequency activity. These instrumental functions of
low-frequency oscillations support a conceptual framework that integrates
numerous earlier findings.
LA  - English
DB  - MTMT
ER  - 

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  -