Fig. 3.

(A) Diagram of the temporal order memory task including the timing of the drug infusions. Illustrated is the square arena containing the stimulus objects. In sample phase 1 two identical objects are presented and following an inter-sample interval two different objects are presented in sample phase 2. Following a retention delay, an object from sample phase 1 and an object from sample phase 2 are presented in the test phase. To examine drug effects on encoding, drug infusions were given prior to sample phase 2. To examine effects on retrieval infusions were given prior to the test phase. (B) The effect of AMPA receptor blockade on temporal order memory. Illustrated for each group is the mean (+SEM) discrimination ratio. **P < 0.01, ***P < 0.001, difference between groups. Bilateral infusion of CNQX into the perirhinal cortex (PRH) or medial prefrontal cortex (PL/IL) given before the sample phase 2 or before the test phase. (C) The effect of unilateral drug infusions into the perirhinal cortex (PRH) and medial prefrontal cortex (PL/IL) in opposite hemispheres, prior to sample phase 2 on temporal order memory. Unilateral drug infusions into the PRH, represented by grey shading, disrupts encoding of the object presented in sample phase 2 (S2) so that the S2 object is represented as a novel object. The object information is sent to the un-infused PL/IL. In the opposite hemisphere the un-infused PRH encodes the objects presented in sample phase 1 (S1) and sample phase 2 (S2) as familiar, and may also encode the relative recency of the object presentation, i.e. that the S1 object is an ‘old’ object, while the S2 object has been encountered relatively recently. This object information is sent to the infused PL/IL, but here the order information cannot be expressed correctly as processing has been disrupted by the drug infusion. The bilateral disruption within the temporal order memory circuit results in impaired discrimination.

Barker and Warburton [109]. Reprinted by permission of John Wiley & Sons, Inc.