PMC

Performance of the amnesic patients with the data for each plotted separately. (A) P01, (B) P02, (C) P03, (D) P04.

Structural MRI scans: coronal sections through the MRI brain scans of each patient, where the damaged hippocampi are indicated by white arrows. Note P01's scan is a FLAIR image, while the other scans are T1 images.

Performance of amnesic patients and control subjects plotted for each condition separately (spatial, non-spatial). (A) Performance of the six control subjects. Error bars are not shown since comparison of performance in spatial and non-spatial conditions is within-subjects. (B) Performance of the four amnesic patients.

Performance of amnesic patients and control subjects, collapsed across condition (spatial or non-spatial). Each block consisted of 50 trials, with presentation of each of the eight patterns occurring pseudorandomly (see Section ). Error bars reflect standard error of the mean (S.E.M.).

Performance of amnesic patients divided into two groups according to strategy (optimal or sub-optimal). (A) Average performance of optimal strategy patients (P01 and P04). These patients adopted a configural associative strategy (see Section /Section for details of strategy analysis) and performed relatively well on the task (average performance during last three blocks: 80%, S.D. 2.9). (B) Average performance of sub-optimal strategy patients (P02 and P03). These patients performed relatively poorly (average performance during last three blocks: 62.7%, S.D. 5.6), failing to adopt a configural strategy and using at best an elemental (i.e. single shape) strategy. The use of this elemental strategy naturally results in superior performance in the non-spatial, as compared to the spatial, condition, although this difference was not statistically significant.

Experimental design: subjects were instructed to play the role of a weather forecaster, and try to learn over the course of the experiment how different “patterns” of shapes on the screen were associated with one of two outcomes, sun or rain (see Section ). Each one of the eight patterns was associated with an outcome in a deterministic fashion (i.e. with 100% probability). In patterns 1–4, the position of the triangle determines the outcome (in this example, although the allocation of shapes to outcomes was changed between subjects). Hence when the triangle appears on the left, the outcome is sun regardless of the shape present in the centre. When the triangle appears on the right, the outcome is always rain. In patterns 5–8, specific shape–shape pairings determine the outcome, with the position of the square being irrelevant. Hence, square together with star is associated with sun, regardless of the position of the square. Conversely, square together with ellipse is always associated with rain. Trials could therefore be divided conceptually into those involving learning of spatial (patterns 1–4), as opposed to non-spatial (patterns 5–8), configural associative information.