John Joseph Downes

Memory for single items, word pairs, and temporal order of different kinds in a patient with selective hippocampal lesions

One kind of between-list and two kinds of within-list temporal order memory were examined in a patient with selective bilateral hippocampal lesions. This damage disrupted memory for all three kinds of temporal order memory, but left item and word pair recognition relatively intact. These findings are inconsistent with claims that (1) hippocampal lesions, like those of the medial temporal lobe (MTL) cortex, disrupt item and word pair recognition, and that (2) hippocampal lesions disrupt temporal order memory and item recognition to the same degree. Not only was word pair recognition intact in the patient, but further evidence indicates that her recognition of other associations between items of the same kind is also spared so retrieval of such associations cannot be sufficient to support within-list temporal order recognition. Rather, as other evidence indicates that the patient is impaired at recognition of associations between different kinds of information, within-list (and possibly between-list) temporal order memory may be impaired by hippocampal lesions because it critically depends on retrieving associations between different kinds of information.

Does Context Discriminate Recollection from Familiarity in Recognition Memory

Five experiments were conducted to examine subjects’ ability to make contextual judgements about recognized items for which they report recollective experience or only familiarity within the context of the experiment. In the first four experiments, subjects were able to make judgements of the spatiotemporal context of items that were accompanied by recollective experience significantly better than for items they merely found familiar. In only one of the four studies did subjects display above-chance performance on spatiotemporal judgements for merely familiar items. A fifth experiment examined the frequency with which subjects report the presence of different kinds of contextual knowledge during a standard recognition experiment. All aspects of contextual knowledge were reported with higher frequencies for recollected items than for items only found familiar, although no single contextual feature was strongly associated with recollective experience. Thus, the five studies together provide converging evidence for the validity of the “recollect-know” distinction in recognition memory and supplement studies that have already demonstrated that the two kinds of response are dissociable. The implications of these data for group comparisons of memory-impaired patients, and the role of context in recognition memory are discussed.

Long-term accelerated forgetting of verbal and non-verbal information in temporal lobe epilepsy.

INTRODUCTION We investigated whether pre-surgical patients with temporal lobe epilepsy (TLE) forget verbal and non-verbal material faster than healthy controls over retention intervals of an hour and 6 weeks, and whether any observed memory loss was associated with structural changes to the hippocampus and/or seizure frequency. METHODS A mixed factorial design compared the performance of 27 patients with TLE and 22 healthy control participants, matched for IQ, age and gender, on tests of story recall and complex figure recall at three delays: immediate, 1 h and 6 weeks. Performance of the patient and control groups was matched at the immediate delay, which enabled comparisons of forgetting rate over the longer delays. RESULTS We found that TLE can affect the acquisition and retention of new memories over a relatively short delay of 1h. This deficit was associated with structural hippocampal abnormality, with a material-specific effect that was particularly evident for the verbal task. We also found evidence of accelerated long-term forgetting in both patient groups, for the verbal and non-verbal tasks. It was demonstrated most strongly on the verbal task by the patients with right lateralized hippocampal sclerosis whose verbal recall was normal at the 1-h delay. Accelerated long-term forgetting was not associated with hippocampal pathology, but was associated with the frequency of epileptic seizures. DISCUSSION The findings from the verbal task in particular provide evidence consistent with an extended period of memory consolidation that can be disrupted by both left and right TLE. The material-specific effects at the 1-h delay only, suggest that the initial consolidation of verbal and non-verbal, information depends on the integrity of the left and right hippocampus, respectively.

Impaired recall of verbal material following rupture and repair of an anterior communicating artery aneurysm

Abstract This paper presents a detailed investigation of the memory impairment suffered by a patient, ROB, following the rupture and repair of an anterior communicating artery aneurysm that damaged her left hemisphere. ROB is severely impaired on standard tests of verbal recall such as paired-associate learning and memory for prose passages. Nevertheless she performs normally on both versions of Warringtons (1984) recognition memory test, and on tests that require recall of visuo-spatial material. She also shows no evidence of confabulation. The discrepancy between recall and recognition performance persists even when attempts are made to ensure that the two types of test are equally “difficult” (cf. Calev, 1984). The impairment does not seem to be caused by inappropriate encoding strategies, since recall performance is not improved by imagery instructions or by levels of processing manipulations (Craik&Tulving, 1975). She also performs normally on implicit memory tests regardless of whether they involve...

Intellectual, mnemonic, and frontal functions in dementia with Lewy bodies: A comparison with early and advanced Parkinson's disease.

Both Parkinsons disease (PD) and dementia with Lewy bodies (DLB) share a common neuropathological marker, the presence of Lewy bodies in brain stem and basal forebrain nuclei. DLB, in addition, is associated with Lewy bodies in the neocortex, and, in its more common form, with Alzheimer-type pathological markers, particularly amyloid plaques. Published neuropsychological studies have focused on the differential profiles of DLB and Alzheimers disease (AD). However, it is presently unclear whether DLB should be classified as a variant of AD or PD. In the present study we compare a healthy age-matched control group with three groups of patients, one with DLB, and two with PD. One of the PD groups was early in the course (PD-E) and the second, more advanced group (PD-A), was matched on severity of cognitive impairment with the DLB group. The results show that DLB was associated with a different pattern of neuropsychological impairment than the PD-A group, particularly in tests believed to be mediated by prefrontal cortical regions.

An exploratory study of the relationship between face recognition memory and the volume of medial temporal lobe structures in healthy young males.

A rigorous new methodology was applied to the study of structure function relationships in the living human brain. Face recognition memory (FRM) and other cognitive measures were made in 29 healthy young male subjects (mean age = 21.7 years) and related to volumetric measurements of their cerebral hemispheres and of structures in their medial temporal lobes, obtained using the Cavalieri method in combination with high resolution Magnetic Resonance Imaging (MRI. Greatest proportional variability in volumes was found for the lateral ventricles (57%) for the cerebral hemispheres (8%) in the mean volumes of the hippocampus, parahippocampal gyrus, amygdala, caudate nucleus, temporal pole and temporal lobe on the right and left sides of the brain. The volumes of the right and left parahippocampal gyrus, temporal pole, temporal lobe, and left hippocampus were, prior to application of the Bonferroni correction to take account of 12 multiple comparisons, significantly correlated with the volume of the corresponding hemisphere(p < 0.05). The volumes of all structures were highly correlated (p < 0.0002 for all comparisons) between the two cerebral hemispheres. There were no positive relationships between structure volumes and FRM score. However, the volume of the right amygdala was, prior to application of the Bonferroni correction to take account of 38~multiple comparisons, found to be significantly smaller in the five most consistent high scorers compared to the five most consistent low scorers (t = 2.77,p = 0.025). The implications for possible relationships between healthy medial temporal lobe structures and memory are discussed.

Temporal order memory in patients with Korsakoff's syndrome and medial temporal amnesia

Two groups of patients with global amnesia resulting either from Korsakoffs syndrome (KS) or from medial temporal lobe (MTL) damage were compared with groups of matched healthy control subjects on a list discrimination paradigm. Item recognition memory was matched across the amnesic and control groups in order to determine whether KS, but not MTL amnesics are disproportionately impaired on list discrimination as predicted by Parkins [Functional significance of etiological factors in human amnesia. In: Squire LR, Butters N, editors. Neuropsychology of memory, 2nd ed. New York: The Guilford Press, 1992] hypothesis. However, both patient groups were impaired disproportionately on the temporal order memory task, which is inconsistent with Parkins hypothesis. It remains possible that the KS patients are more disproportionately impaired than those with MTL damage because both patient groups performed at floor on the list discrimination task. The results are consistent with theories that postulate a critical role for the hippocampus in the kind of associative memory which underlies memory for temporal order, but not in recognition of single items or arbitrary associations between items of similar kinds.

The pre-exposure technique: Enhancing the effects of errorless learning in the acquisition of face–name associations

In an earlier paper (Downes et al., 1997), we demonstrated how the beneficial effects of imagery in a face-name association learning task could be enhanced further by the simple expedient of pre-exposing faces for a brief period prior to the introduction of the names to be associated. The present study examines whether the technique of errorless learning, recently applied in neuropsychological rehabilitation, might also benefit from pre-exposure. The rationale for hypothesising such an interaction follows from the speculation raised in our earlier work that the two techniques may be operating at different stages of learning—pre-exposure at registration/consolidation stages and errorless learning at retrieval. Accordingly, a group of brain-injured memory-impaired subjects was given four sets of face-name associations to learn under different experimental conditions. Two of these conditions compared errorless and errorful conditions, and two combined errorless learning with different versions of the pre-exposure technique. The results confirm that, in terms of the number of names learned on the first trial and the number of trials to criterion, errorless learning was significantly superior to errorful learning. Furthermore, both preexposure conditions in combination with errorless learning resulted in a significant enhancement of learning compared to errorless learning alone. Thus, as with imagery, although significant gains in performance are evident when errorless learning is used, further enhancement can be achieved by combining it with preexposure.

Validation of the Wechsler Memory Scale-III in a population of people with intractable temporal lobe epilepsy.

The Wechsler Memory Scale-Third Edition (WMS-III) was developed to overcome the limitations of the Wechsler Memory Scale-Revised and is now routinely used for pre-surgical assessment of memory for patients considering elective surgery for the relief of temporal lobe epilepsy (TLE). We investigated the validity of this relatively new measure in a population of people with resistant TLE. The sample consisted of 99 patients with a diagnosis if TLE in which the epileptogenic focus was clearly identified and localised to either the right or left hemisphere. Patients underwent a full neuropsychological assessment as part of their pre-surgical investigation, including the WMS-III. Patients with right temporal focus had significantly lower scores on the visual immediate and delayed indices of the WMS-III than they did on the corresponding auditory indices. The left temporal focal epilepsy group, however, showed no significant disparity between auditory and visual scores. The overall scores of the WMS-III were significantly lower than the normative data from the WMS-III standardisation samples. Like its predecessor the Wechsler Memory Scale-Revised, the WMS-III has limited value in identifying particular memory deficits associated with either left and right temporal lobe focus. The results of the WMS-III show that it is capable of lateralising to right hemispheric impairment but is more problematic in the assessment of left hemispheric impairment. The visual verbal discrepancy has questionable validity. The search for reliable and valid measures to distinguish between left and right temporal epileptic focus continues.

Remembering and knowing in a patient with preserved recognition and impaired recall

ROB is a patient who has a severe deficit in recalling recently presented verbal material following rupture and repair of an anterior communicating artery aneurysm [Hanley JR, Davies ADM, Downes J, Mayes A. Cognitive Neuropsychology 1994;11:543-78; Hanley JR, Davies ADM. In: Parkin A, editor. Case Studies in the Neuropsychology of Memory. Hillsdale, NJ: Lawrence Erlbaum, 1997. p. 111-26]. Despite this, her performance on tests of recognition memory is comfortably within the normal range. In the present series of experiments, we investigated whether or not ROBs performance on tests of recognition memory might be associated with a disproportionately large number of correct decisions made on the basis of familiarity rather than contextual retrieval [e.g. Mandler G. Psychological Review 1980;87:252-71]. Contrary to this hypothesis, the results showed that ROB made a high proportion of remember decisions relative to know decisions in recognition [cf. Gardiner JM. Memory & Cognition 1988;16:309-13] and produced a high recollection score when conscious recollection and familiarity were placed in opposition to one another [cf. Jacoby LL, Woloshyn V, Kelley C. Journal of Experimental Psychology: General 1989;118:115-25.]. ROBs recognition memory performance therefore appears to be qualitatively as well as quantitatively similar to that found in the normal population. As ROB has suffered damage to both the fornix and the anterior thalamus, the results of the present study are consistent with the claim that damage to the extended hippocampal system has a much more severe effect on recall than on recognition [Aggleton JP, Shaw C. Neuropsychologia 1996;34:51-62; Aggleton JP, Saunders RC. Memory 1997;5:49-71]. The present results provide no support, however, for the additional suggestion [Aggleton JP, Brown MW. Behavioral and Brain Sciences 1999;22:425-56.] that the extended hippocampal system is necessary for recognition memory decisions that are based on contextual retrieval.