Associative representational plasticity in the auditory cortex: resolving conceptual and empirical problems

Associative representational plasticity (ARP) concerns the systematic modification of neuronal responses to a stimulus dimension that involves the learning of relationships between a conditioned stimulus (CS) on that dimension with a behaviorally significant reinforcer. Most extensively studied for acoustic frequency in the primary auditory cortex (A1), the dominant findings are a CS-specific increase in response and a CS-directed shift of tuning. Extensive characterization of this ARP suggests that it serves as part of the substrate of specific memory. Ohl and Scheich have argued that neither the form nor suggested function is valid. They claim that the form of ARP is a CS-specific decreased response, and the function is lateral contrast enhancement. An analysis of their arguments reveals that their claims rest on problematic assumptions, confusions, and failure to obtain behavioral validation of associative learning. While new forms and possible functions of ARPs may be discovered, they have not yet been substantiated.