Successive-signal biasing for a learned sound sequence.
Adult rats were trained to detect the occurrence of a two-element sound sequence in a background of nine other nontarget sound pairs. Training resulted in a modest, enduring, static expansion of the cortical areas of representation of both target stimulus sounds. More importantly, once the initial stimulus A in the target A-B sequence was presented, the cortical "map" changed dynamically, specifically to exaggerate further the representation of the "anticipated" stimulus B. If B occurred, it was represented over a larger cortical area by more strongly excited, more coordinated, and more selectively responding neurons. This biasing peaked at the expected time of B onset with respect to A onset. No dynamic biasing of responses was recorded for any sound presented in a nontarget pair. Responses to nontarget frequencies flanking the representation of B were reduced in area and in response strength only after the presentation of A at the expected time of B onset. This study shows that cortical areas are not representationally static but, to the contrary, can be biased moment by moment in time as a function of behavioral context.
Zhou
Xiaoming
X
School of Life Sciences, Institute of Cognitive Neuroscience, East China Normal University, Shanghai 200062, China. xmzhou@bio.ecnu.edu.cn
de Villers-Sidani
Etienne
E
Panizzutti
Rogerio
R
Merzenich
Michael M
MM
D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000166:cytology / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D001931:Brain Mapping; D004192:Discrimination, Psychological / Q000502:physiology; D005260:Female; D007858:Learning / Q000502:physiology*; D008959:Models, Neurological; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013016:Sound