Visually induced gamma-band responses in human electroencephalographic activity ? a link to animal studies

Abstract

Visual presentation of an object produces firing patterns in cell assemblies representing the features of the object. Based on theoretical considerations and animal experiments, it has been suggested that the binding of neuronal representations of the various features is achieved through synchronization of the oscillatory firing patterns. The present study demonstrates that stimulus-induced gamma-band responses can be recorded noninvasively from human subjects attending to a single moving bar. This finding indicates the synchronization of oscillatory activity in a large group of cortical neurons. Gamma-band responses were not as apparent in the presence of two independently moving stimuli, suggesting that the neuronal activity patterns of different objects are not synchronized. These results open a new paradigm for investigating the mechanisms of feature binding and association building in relation to subjective perception.

Selective visual-spatial attention alters induced gamma band responses in the human EEG

“…It is currently unclear as to what accounts for the differences in the reported frequency ranges across human gamma band studies. An increase of gamma power was reported for coherently moving lines giving the impression of a waterfall at 35±45 Hz (Lutzenberger et al, 1995), for a coherently moving long bar at 40±96 Hz (Mu Èller et al, 1996) which was replicated for the same frequency band (Mu Èller et al, 1997b), for a visual search task around 40 Hz (Tallon-Baudry et al, 1997a), after the short presentation of illusionary and real triangles at 30 Hz (Tallon et al, 1995) which was replicated at 40 Hz (TallonBaudry et al, 1996(TallonBaudry et al, , 1997b and, recently, for a delayedmatching-to-sample task at 24±60 Hz (Tallon-Baudry et al, 1998). It seems likely that both the variance in tasks and stimulation account for the variety of results.…”

“…Since the present analysis focused on non phase-locked oscillatory activity, the evoked response (i.e. the VEP) was subtracted from each trial (see also Mu Èller et al, 1996, for a similar procedure). Spectral analysis was then calculated on artifact-free trials by means of a FFT algorithm developed by .…”

“…In human EEG, gamma band responses were induced by coherently moving lines giving the impression of a waterfall (Lutzenberger et al, 1995), by the short presentation of illusory Kanizsa and real triangles (Tallon et al, 1995;Tallon-Baudry et al, 1997b), by a visual search task (Tallon-Baudry et al, 1997a), by a coherently moving long bar (Mu Èller et al, 1996(Mu Èller et al, ,1997a and by the perception of a Gestalt (Keil et al, 1999). In addition, induced gamma band responses were linked to cognitive processes, such as the processing of words Pulvermu Èller et al, , 1997, language and non-language stimuli (Eulitz et al, 1996) and, recently, to short-term memory processes during a delayed matching-to-sample task (Tallon-Baudry et al, 1998).…”

Processing of affective pictures modulates right-hemispheric gamma band EEG activity

“…By synchronizing their ®ring patterns, neurons in a cell assembly would produce EEG activity in the gamma band when the assembly is ignited (Eckhorn et al, 1990;Singer and Gray, 1995;Pulvermu Èller et al, 1997). In humans, non-invasive electro-(EEG) and magnetoencephalographic (MEG) recordings have provided evidence that cortical activity in the gamma band range (above 20 Hz) is modulated by (a) the features of a stimulus (Mu Èller et al, 1996;Tallon et al, 1995;Mu Èller et al, 1997;Tallon-Baudry et al, 1997b), by (b) visual spatial attention (Mu Èller, 1998;Gruber et al, 1999), and (c) may represent the perception of a Gestalt (Tallon-Baudry et al, 1997a,b;Keil et al, 1999). In addition, power in the gamma band was enhanced during the active representation of an object in short-term memory during the delay of a delayed-matching-to-sample task (Tallon-Baudry et al, 1998).…”

“…As of today, research on cortical emotional responses in the frequency domain was mainly focused on alpha desynchronization (see Davidson, 1995, for an overview). Alpha desynchronization, however, is a poor predictor for measuring the activity of cortical networks since topographical distributions of alpha and high frequency responses are not inversely related in an one-by-one fashion (Mu Èller et al, 1996;Mu Èller et al, 1997;Mu Èller, 1998;Tallon-Baudry et al, 1998). Ray and Cole (1985), for instance reported higher beta activity (16± 24 Hz) in right hemisphere temporal and parietal areas, whereas no effect was found in the alpha band to re¯ect emotional processes.…”