Larry Leach

Clustering and switching on verbal fluency tests in Alzheimer's and Parkinson's disease

Two components of verbal fluency performance--clustering (i.e., generating words within subcategories) and switching (i.e., shifting between subcategories)--were examined in patients with dementia of the Alzheimer type (DAT), patients with dementia with Parkinsons disease (DPD), nondemented patients with Parkinsons disease (NPD), and demographically matched controls. The DAT and DPD groups were impaired in the number of words generated on both phonemic and semantic fluency. The DAT group produced smaller clusters on both tasks and switched less often on semantic fluency than controls. The DPD group switched less often on both tasks and produced smaller clusters on phonemic fluency than controls. The NPD group was not impaired on any fluency variable. Thus, the total number of words generated on phonemic and semantic fluency did not discriminate the dementia groups from their respective control groups, but measures of clustering and switching did. This differential pattern of performance provides evidence for the potential usefulness of measures of switching and clustering in the assessment of dementia.

Different Patterns of Autobiographical Memory Loss in Semantic Dementia and Medial Temporal Lobe Amnesia: a Challenge to Consolidation Theory

Temporally graded retrograde memory loss, with a disproportionate impairment of recent relative to remote memories, is considered a hallmark of medial temporal lobe amnesia. According to consolidation theory, the hippocampal complex, which includes the hippocampal formation, parahippocampal gyrus, the entorhinal and perirhinal cortex, plays a time-limited role in memory, needed only until consolidation in the neocortex is complete (Squire, Psychological Review 1992; 99: 195–231). Recent support for this theory comes from findings of a reverse gradient in people with semantic dementia with neocortical degeneration but a relatively preserved hippocampal complex (Hodges and Graham, Neuropsychologia 1998; 36: 803–25). Consolidation theory is challenged by evidence that remote autobiographical memory is not always spared in amnesia (Nadel and Moscovitch, Current Opinion in Neurobiology 1997; 7: 217–27) and that semantic memory becomes highly personalized in semantic dementia (Snowden et al., Memory 1995; 3: 225–46). According to Nadel and Moscovitch, the hippocampal complex is needed to retain and retrieve detailed memories of autobiographical episodes no matter how old they are. To test consolidation theory against the opposing view, we investigated the role of the hippocampal complex in recent and remote autobiographical and personal semantic memory by contrasting the memory of a semantic dementia patient, EL, with that of an amnesic patient, KG, using family photographs as recall cues. KG demonstrated a complete loss of autobiographical episodes with a sparing of autobiographical facts; EL demonstrated well-preserved memory for episodes with a reverse gradient for personally relevant names. The influence of autobiographical significance on memory for names of public figures was examined further by comparing the effect that familiarity and recollection had on recognition of names of famous people and famous places. EL’s memory was influenced by autobiographical significance, whereas KC’s was not. We propose that the hippocampal complex plays a permanent role in the storage and retrieval of autobiographical episodes and that autobiographical significance may affect semantic representations.

Aging and Response Inhibition: Normative Data for the Victoria Stroop Test

ABSTRACT Increased difficulty with response inhibition occurs with age, although there is some controversy as to whether increased interference on Stroop tasks reflects difficulties with response inhibition or simply reflects generalized cognitive slowing. The Victoria Stroop Test (VST) is a brief, easily administered, psychometrically sound version of Stroops original task. Performance on the VST by adults across a wide age span was examined to determine the association between age and various measures of interference. In addition, normative data for the VST were calculated. Participants were 272 healthy, community-dwelling adults age 18 to 94. Age and speed were negatively correlated on all trials of the VST. Importantly, however, interference scores that were corrected for baseline slowing remained highly correlated with age. Similarly, age and error scores on the interference trial were positively correlated, indicating decreased accuracy with age. These findings suggest that increased interference on Stroop tasks with age is not accounted for by simple cognitive slowing and more likely reflects other cognitive changes, such as decreased response inhibition. The VST has a number of administrative and psychometric strengths, and the provision of normative data should enhance its potential for clinical and research applications.

PDA and smartphone use by individuals with moderate-to-severe memory impairment: Application of a theory-driven training programme

We describe a structured, theory-driven training programme for individuals with moderate-to-severe memory impairment in the use of emerging commercial technology. We demonstrate its application to 10 individuals with memory impairment from a variety of aetiologies. A within-subject, ABAB multi-case experimental design was used to evaluate the impact of personal digital assistant or smartphone use on day-to-day memory functioning at baseline, immediately post-intervention, at return to baseline, and at short-term follow-up (range = 3–8 months). An errorless fading-of-cues protocol enabled all participants to acquire the skill set necessary to operate their PDA or smartphone independently. All 10 individuals showed robust improvement in day-to-day functioning post-intervention as quantified across a number of ecologically valid questionnaire and task-based measures. This was further corroborated by family members with whom six of the participants resided. These findings demonstrate that individuals with moderate-to-severe memory impairment can acquire the skills necessary to independently, flexibly and broadly apply commercial technology to support their everyday memory functioning. Moreover the findings confirm that the gap between individuals with memory impairment and potent emerging technology can be closed by the application of a systematic theory-driven training programme.

The use of clock tests in schizophrenia

Though clock drawing tests are well recognized as measures of cognitive function, there is little data on the performance of patients with schizophrenia. We compared 24 patients with schizophrenia to 24 healthy, age-matched controls on clock drawing, copying, and reading. Patients with schizophrenia performed significantly worse on clock drawing and copying despite the fact that the groups had similar scores on the MMSE. Worse performance was associated with higher scores on the BPRS. Clock drawing and copying may be useful for the assessment of cognition in schizophrenia, and the monitoring of cognitive changes associated with antipsychotic medication.

Hippocampal Complex Contribution to Retention and Retrieval of Recent and Remote Episodic and Semantic Memories: Evidence from Behavioral and Neuroimaging Studies of Healthy and Brain-Damaged People

For over a hundred years, it has been accepted that remote memories are less vulnerable to disruption than are recent memories. The standard consolidation model posits that the hippocampus and related structures are temporary memory structures, necessary for acquisition, retention, and retrieval of all explicit (declarative) memories until they are consolidated elsewhere in the brain. We review lesion and neuroimaging evidence showing that important distinctions exist among different types of explicit memory and the structures that mediate them. We argue that retention and retrieval of detailed, vivid autobiographical memories depend on the hippocampal system no matter how long ago they were acquired. Semantic memories, on the other hand, benefit from hippocampal contribution for some time before they can be retrieved independently of the hippocampus. Even semantic memories, however, can have episodic elements associated with them which continue to depend on the hippocampus. In short, the evidence reviewed suggests strongly that the function of the hippocampus (and possibly of related limbic structures) is to help encode, retain, and retrieve experiences, no matter how long ago the events comprising the experience occurred. We conclude that the evidence favors a multiple trace theory (MTT) of memory over the traditional model, and we indicate what future work is needed to resolve disputes.

Recollection and familiarity for public events in neurologically intact older adults and two brain-damaged patients

Despite extensive investigations of the role of recollection and familiarity on laboratory-acquired memories, there is a dearth of such research on memories formed in real life settings. We used the Remember/Know paradigm to investigate the relative contribution of recollection and familiarity processes to memory of public historical events reported in the media across the life span of two groups of neurologically intact older adults (old-old: 74-85, young-old: 58-69) and on two patients with brain damage. First, in neurologically intact participants, recollection rates decreased as a function of time elapsed since the event occurred, at a significantly higher rate than the corresponding decrease in familiarity or global memory. Second, consistent with the hypothesis that memories become increasingly semantic as they age, and that recollection is selectively impaired in older adults, across decades, old-old participants exhibited lower recollection, but not familiarity, relative to young-old participants. Finally, as a demonstration of how this procedure may be applied to studies of clinical populations, we tested two patients, one with medial temporal lesions and another with relative sparing of the medial temporal lobes, but with anterior temporal damage. We found that recollection was disproportionately impaired relative to familiarity across most of the life span in the patient with medial temporal lesions severely while recollection was relatively intact in the patient with anterior lateral temporal damage. We discuss the present results in the context of neuroanatomical and process-oriented theories of how memories age.

Perceptual Priming of Proper Names in Young and Older Normal Adults and a Patient With Prosopanomia

The purpose of this study was to determine if normal participants and a patient with prosopanomia can be perceptually primed for proper names. To this end, 2 experiments were conducted. In Experiment 1, normative data were collected on 4 proper-name priming tasks. The variables of levels of processing at encoding and age were manipulated. Robust priming results were obtained that were not influenced by either of these variables. The results of Experiment 2 indicated that prosopanomic patient N.G. demonstrated normal repetition priming, despite her marked impairment in deliberate retrieval of person and city names. These results are interpreted in terms of a dissociation between explicit and implicit memory for proper names and suggest that the deficit in prosopanomia only involves deliberate access to the name; access to presemantic representations of the visual word form remains intact.

A re-examination of Montreal Cognitive Assessment (MoCA) cutoff scores

The Montreal Cognitive Assessment (MoCA; Nasreddine et al., 2005) is a cognitive screening tool that aims to differentiate healthy cognitive aging from Mild Cognitive Impairment (MCI). Several validation studies have been conducted on the MoCA, in a variety of clinical populations. Some studies have indicated that the originally suggested cutoff score of 26/30 leads to an inflated rate of false positives, particularly for those of older age and/or lower education. We conducted a systematic review and meta‐analysis of the literature to determine the diagnostic accuracy of the MoCA for differentiating healthy cognitive aging from possible MCI.

Long-term maintenance of smartphone and PDA use in individuals with moderate to severe memory impairment

In an earlier paper we described a structured, theory-driven training programme which was administered to 10 individuals with moderate-to-severe memory impairment. All individuals received an errorless-fading-of-cues protocol in the use of personal digital assistants (PDAs) or smartphones (Svoboda, Richards, Leach, & Mertens, 2012) and demonstrated generalisation of acquired skills to day-to-day memory challenges. Maintenance of intervention gains over the long-term is another indicator of successful generalisation. Here we present the maintenance of device use in the same group of individuals 12 to 19 months after programme completion. A within-subject, ABABB multi-case experimental design was used to evaluate the impact of PDA or smartphone use on day-to-day memory functioning at baseline, immediately post-intervention, at return to baseline, and at short-term and long-term follow-up. Results presented here focus predominantly on long-term follow-up. All 10 individuals showed maintenance of gains in day-to-day functioning as quantified across several ecologically valid questionnaire and task-based measures. This was corroborated by family members with whom six of the participants resided. This study further demonstrates the programmes clinical effectiveness in enabling individuals with moderate-to-severe memory impairment to function more independently and with greater confidence up to 19 months following programme completion.