Ž . International Journal of Psychophysiology 35 2000 95124 Brain oscillations in perception and memory E. Bas ¸ ar a,b,  , C. Bas ¸ ar-Eroglu c , S. Karakas ¸ b,d , M. Schurmann a ˘ ¨ a Institute of Physiology, Medical Uni  ersity Lubeck, 23538, Lubeck, Germany ¨ ¨ b ¨ TUBITAK Brain Dynamics Research Unit, Ankara, Turkey c Institute of Psychology and Cognition Research, 28334, Bremen, Germany d Institute of Experimental Psychology, Hacettepe Uni  ersity, Beytepe, Ankara, Turkey Received 23 March 1999; accepted 23 March 1999 Abstract Gamma oscillations, now widely regarded as functionally relevant signals of the brain, illustrate that the concept of event-related oscillations bridges the gap between single neurons and neural assemblies. Taking this concept further, we review experiments showing that oscillatory phenomena such as alpha, theta, or delta responses to events are strongly interwoven with sensory and cognitive functions. This review argues that selecti  ely distributed delta, theta, alpha, and gamma oscillatory systems act as resonant communication networks through large populations of neurons. Thus, oscillatory processes might play a major role in relation with memory and integrati  e functions. A new ‘neurons-brain’ doctrine is also proposed to extend the neuron doctrine of Sherrington.  2000 Elsevier Science B.V. All rights reserved. Ž . Keywords: Memory; Brain oscillations delta, theta, alpha, gamma ; Evoked potentials; Event-related potentials; Sensory process- ing; Cognitive processing; Distributed networks 1. Introduction 1.1. Aim of the report ‘During the ‘Decade of the Brain’ brain science is coming to terms with its ultimate problem: understanding the mechanisms by which the im-  Corresponding author. Tel.: 49-451-500-4170; fax: 49- 451-500-4171. Ž . E-mail address: ebasar@physio.mu-luebeck.de E. Bas ¸ ar mense number of neurons in the human brain interact to produce the higher cognitive functions’ Ž . Freeman, 1998 . As one of the candidate mecha- nisms, oscillatory neuroelectric acti  ity has recently attracted much interest. In particular, this holds for synchronous gamma activity in spatially dis- tributed cells. In this framework, the present re- view has several aims, namely: 1. To survey functionally-related findings in os- cillatory brain acti  ity in the frequency range 0167-876000$ - see front matter  2000 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 1 6 7 - 8 7 6 0 99 00047-1