E. A. Gaffan

The Roles of Perirhinal Cortex, Postrhinal Cortex, and the Fornix in Memory for Objects, Contexts, and Events in the Rat:

Investigation of the anatomical substructure of the medial temporal lobe has revealed a number of highly interconnected areas, which has led some to propose that the region operates as a unitary memory system. However, here we outline the results of a number of studies from our laboratories, which investigate the contributions of the rats perirhinal cortex and postrhinal cortex to memory, concentrating particularly on their respective roles in memory for objects. By contrasting patterns of impairment and spared abilities on a number of related tasks, we suggest that perirhinal cortex and postrhinal cortex make distinctive contributions to learning and memory: for example, that postrhinal cortex is important in learning about within-scene position and context. We also provide evidence that despite the strong connectivity between these cortical regions and the hippocampus, the hippocampus, as evidenced by lesions of the fornix, has a distinct function of its own—combining information about objects, positions, and contexts.

Elemental and configural visual discrimination learning following lesions to perirhinal cortex in the rat.

Rats were tested in a series of two-choice visual discrimination tasks in a computer-controlled testing apparatus. The discriminations used a range of discriminanda, which varied in complexity. The discriminations included relatively simple form discriminations, more complex form discriminations and discriminations between compound stimuli that shared many features. It was found that rats with perirhinal cortex lesions were unimpaired in all discriminations except those that involved the compound stimuli with overlapping features. Using these stimuli, rats with perirhinal cortex lesions were unimpaired when the stage of learning did not necessitate discriminating stimuli on the basis of more than one feature. However, when efficient performance of the task needed the configuration of more than one feature to be taken into account, perirhinal lesioned rats were impaired. These results are interpreted as revealing the role of the perirhinal cortex in providing multifeature information about the properties of visual objects.

Anterior rhinal cortex and amygdala: dissociation of their contributions to memory and food preference in rhesus monkeys.

Rhesus monkeys were trained on 2 versions of delayed nonmatching-to-sample, one with multiple pairs of objects and the other with a single pair, to evaluate their ability to remember objects. They then received either bilateral aspiration lesions of the anterior rhinal cortex or bilateral excitotoxic lesions of the amygdala, or were retained as unoperated controls. On re-presentation of the multiple-pair task, monkeys with anterior rhinal cortex lesions failed to show the improvement observed in both other groups in remembering the objects over delay intervals ranging from 10 to 60 s. Also, monkeys with anterior rhinal cortex lesions were impaired relative to the controls in relearning the single-pair version of the task. Conversely, on a formal test of food preference, monkeys with amygdala lesions showed abnormal patterns of food choice, whereas monkeys with anterior rhinal cortex lesions did not. Visual memory impairments formerly attributed to amygdala damage are probably due to the rhinal cortex damage associated with aspiration lesions of the amygdala.

The Performance of Postencephalitic Amnesic Subjects on Two Behavioural Tests of Memory: Concurrent Discrimination Learning and Delayed Matching-To-Sample

The performance of a group of three postencephalitic subjects with anterograde amnesia was examined on a series of concurrent visual discrimination problems and on a test of visual recognition, delayed matching-to-sample. These tests were chosen as they have been used to assess experimental models of anterograde amnesia in nonhuman primates. In comparison with a group of normal subjects the postencephalitic group were impaired on the more difficult concurrent discrimination problems. They also performed poorly on the matching-to-sample task when given lists of items to remember or given increased retention intervals. The pattern of performance of the postencephalitic group matched closely that of a group of Korsakoff subjects, indicating that these behavioural tests are equally sensitive to different types of anterograde amnesia.

Reward, novelty and spontaneous alternation

It has been suggested that rats’ propensity for “win-shift” behaviour in spatial memory and spontaneous alternation tests reflects a species-specific foraging strategy which leads them to avoid places where they have recently found food. An alternative explanation is that they avoid places which are familiar. In three experiments using a T-maze, we evaluated these accounts by comparing the probability of avoiding or re-entering a recently visited arm, as a function of whether food had or had not been found on the previous visit. Each rat received a series of 16 exposure-test trial pairs over 8 days. Neither alternation nor repetition of the previous choice was differentially reinforced. Experiments I and II forced rats to enter a specific arm before a subsequent choice, and differed in the overall probability of reward; in Experiment III all choices were free. In all three experiments the probability of alternating was greater after nonreward than after reward. This effect occurred more reliably on later tests within a day, little difference appearing on earlier tests. It was concluded that there was no evidence for a spontaneous “win-shift” tendency as such, and that these and other results can be adequately accounted for by a combination of exploratory tendencies (spontaneous alternation) and the conventional effects of reward.

Experimental functional analyses for challenging behavior: a study of validity and reliability.

The convergent validity of an experimental (analog) functional analysis was investigated by a comparison of three separate ways of interpreting the data derived from such an assessment: two previously published methods and the criterion Z method derived by the authors. Data from the experimental functional analysis of the challenging behavior(s) of 27 individuals with intellectual disabilities were analyzed to assess agreement between the three forms of interpretation. The test-retest reliability of all three methods over periods of 2 weeks, 1 month, and 3 months was also calculated. The results suggest that the methods of interpreting function from experimental assessments can give different results and that the test-retest reliability of the experimental functional analyses is poor. The implications of these findings are discussed in relation to clinical practice.

The Huntington's Disease health‐related Quality of Life questionnaire (HDQoL): a disease‐specific measure of health‐related quality of life

Hocaoglu MB, Gaffan EA, Ho AK. The Huntingtons disease health‐related quality of life questionnaire: a disease‐specific measure of health‐related quality of life.

Health-related quality of life in Huntington's disease patients: a comparison of proxy assessment and patient self-rating using the disease-specific Huntington's disease health-related quality of life questionnaire (HDQoL)

Huntington’s disease (HD) is a fatal, neurodegenerative disease for which there is no known cure. Proxy evaluation is relevant for HD as its manifestation might limit the ability of persons to report their health-related quality of life (HrQoL). This study explored patient–proxy ratings of HrQoL of persons at different stages of HD, and examined factors that may affect proxy ratings. A total of 105 patient–proxy pairs completed the Huntington’s disease health-related quality of life questionnaire (HDQoL) and other established HrQoL measures (EQ-5D and SF-12v2). Proxy–patient agreement was assessed in terms of absolute level (mean ratings) and intraclass correlation. Proxies’ ratings were at a similar level to patients’ self-ratings on an overall Summary Score and on most of the six Specific Scales of the HDQoL. On the Specific Hopes and Worries Scale, proxies on average rated HrQoL as better than patients’ self-ratings, while on both the Specific Cognitive Scale and Specific Physical and Functional Scale proxies tended to rate HrQoL more poorly than patients themselves. The patient’s disease stage and mental wellbeing (SF-12 Mental Component scale) were the two factors that primarily affected proxy assessment. Proxy scores were strongly correlated with patients’ self-ratings of HrQoL, on the Summary Scale and all Specific Scales. The patient–proxy correlation was lower for patients at moderate stages of HD compared to patients at early and advanced stages. The proxy report version of the HDQoL is a useful complementary tool to self-assessment, and a promising alternative when individual patients with advanced HD are unable to self-report.

Memory for feeding in rats' spatial and visual choice behaviour.

Four experiments with mazes examined the effects of feeding upon rats’ subsequent choice between spatially or visually distinct alternatives. It is concluded that rats can recall both whether any food remained at the cessation of feeding (nondepletion) and whether or not feeding was interrupted; both features can be associated with the place where they occurred. The memory of nondepleted food evokes an unlearned tendency to return to the place where it was present (“win–stay” behaviour). The memory of interruption transiently had a similar effect in naive animals but eventually exerts a more nonspecific influence, which facilitates not only win–stay learning but its opposite, win–shift. The nondepletion effect was also obtained when the alternatives were defined by a visual cue (brightness) rather than spatial location. The determinants of staying and shifting are discussed in terms of reward memory and exploration.

Pigeons' withdrawal from an appetitive conditioned inhibitor under two training procedures

The approach-withdrawal behaviour of pigeons to a red keylight was measured under three conditions; a negative contingency (NC) between keylight and food reinforcement, a CI or conditioned inhibition procedure where the keylight was non-reinforced in compound with a tone which was reinforced when presented alone, and a random control procedure (RC). The keylight-food contingencies in CI and NC were identical, and keylight and food presentation frequency were the same in all conditions. Subsequently the effect of adding the red keylight to a novel CS+ during or after excitatory conditioning was examined (summation test of inhibition). The inhibitory procedures, CI and NC, generally yielded similar functions for the acquisition of withdrawal, and the results of the withdrawal and summation measures were positively correlated. The implications of the results for theories of the acquisition and behavioural action of conditioned inhibitors are discussed.