Temporal order memory deficits prior to clinical diagnosis in Huntington's disease

LASSI-L detects early cognitive changes in pre-motor manifest Huntington's disease: a replication and validation study

Background and objectives

Cognitive decline is an important early sign in pre-motor manifest Huntington's disease (preHD) and is characterized by deficits across multiple domains including executive function, psychomotor processing speed, and memory retrieval. Prior work suggested that the Loewenstein-Acevedo Scale for Semantic Interference and Learning (LASSI-L)-a verbal learning task that simultaneously targets these domains - could capture early cognitive changes in preHD. The current study aimed to replicate, validate and further analyze the LASSI-L in preHD using larger datasets.

Methods

LASSI-L was administered to 50 participants (25 preHD and 25 Healthy Controls) matched for age, education, and sex in a longitudinal study of disease progression and compared to performance on MMSE, Trail A & B, SCWT, SDMT, Semantic Fluency (Animals), and CVLT-II. Performance was then compared to a separate age-education matched-cohort of 25 preHD participants. Receiver operating curve (ROC) and practice effects (12 month interval) were investigated. Group comparisons were repeated using a preHD subgroup restricted to participants predicted to be far from diagnosis (Far subgroup), based on CAG-Age-Product scaled (CAPs) score. Construct validity was assessed through correlations with previously established measures of subcortical atrophy.

Results

PreHD performance on all sections of the LASSI-L was significantly different from controls. The proactive semantic interference section (PSI) was sensitive (p = 0.0001, d = 1.548), similar across preHD datasets (p = 1.0), reliable on test-retest over 12 months (spearman rho = 0.88; p = <0.00001) and associated with an excellent area under ROC (AUROC) of 0.855. In the preHD Far subgroup comparison, PSI was the only cognitive assessment to survive FDR < 0.05 (p = 0.03). The number of intrusions on PSI was negatively correlated with caudate volume.

Discussion

The LASSI-L is a sensitive, reliable, efficient tool for detecting cognitive decline in preHD. By using a unique verbal learning test paradigm that simultaneously targets executive function, processing speed and memory retrieval, the LASSI-L outperforms many other established tests and captures early signs of cognitive impairment. With further longitudinal validation, the LASSI-L could prove to be a useful biomarker for clinical research in preHD.

Mutation-related magnetization-transfer, not axon density, drives white matter differences in premanifest Huntington disease: Evidence from in vivo ultra-strong gradient MRI

White matter (WM) alterations have been observed in Huntington disease (HD) but their role in the disease-pathophysiology remains unknown. We assessed WM changes in premanifest HD by exploiting ultra-strong-gradient magnetic resonance imaging (MRI). This allowed to separately quantify magnetization transfer ratio (MTR) and hindered and restricted diffusion-weighted signal fractions, and assess how they drove WM microstructure differences between patients and controls. We used tractometry to investigate region-specific alterations across callosal segments with well-characterized early- and late-myelinating axon populations, while brain-wise differences were explored with tract-based cluster analysis (TBCA). Behavioral measures were included to explore disease-associated brain-function relationships. We detected lower MTR in patients' callosal rostrum (tractometry: p = .03; TBCA: p = .03), but higher MTR in their splenium (tractometry: p = .02). Importantly, patients' mutation-size and MTR were positively correlated (all p-values < .01), indicating that MTR alterations may directly result from the mutation. Further, MTR was higher in younger, but lower in older patients relative to controls (p = .003), suggesting that MTR increases are detrimental later in the disease. Finally, patients showed higher restricted diffusion signal fraction (FR) from the composite hindered and restricted model of diffusion (CHARMED) in the cortico-spinal tract (p = .03), which correlated positively with MTR in the posterior callosum (p = .033), potentially reflecting compensatory mechanisms. In summary, this first comprehensive, ultra-strong gradient MRI study in HD provides novel evidence of mutation-driven MTR alterations at the premanifest disease stage which may reflect neurodevelopmental changes in iron, myelin, or a combination of these.

Application of Real and Virtual Radial Arm Maze Task in Human

Virtual Reality (VR) emerges as a promising technology capable of creating different scenarios in which the body, environment, and brain are closely related, proving enhancements in the diagnosis and treatment of several spatial memory deficits. In recent years, human spatial navigation has increasingly been studied in interactive virtual environments. However, navigational tasks are still not completely adapted in immersive 3D VR systems. We stipulate that an immersive Radial Arm Maze (RAM) is an excellent instrument, allowing the participants to be physically active within the maze exactly as in the walking RAM version in reality modality. RAM is a behavioral ecological task that allows the analyses of different facets of spatial memory, distinguishing declarative components from procedural ones. In addition to describing the characteristics of RAM, we will also analyze studies in which RAM has been used in virtual modality to provide suggestions into RAM building in immersive modality.

The effect of interference on temporal order memory in individuals with Parkinson's disease

Memory for the temporal order of items or events in a sequence has been shown to be impaired in older adults and individuals with Parkinson's disease (PD). The present study examined the effects of high and low interference on temporal order memory in individuals diagnosed with PD (n=20) and demographically similar healthy older adults (n=20) utilizing a computerized task used in previously published studies. During the sample phase of each trial, a series of eight circles were randomly presented one at a time in eight different spatial locations. Participants were instructed to remember the sequence in which the circles appeared in the locations. During the choice phase, participants were presented with two circles in two different locations and were asked to indicate which circle appeared earliest in the sample phase sequence. The two circles were separated by one of four possible temporal separation lags (0, 2, 4, and 6), defined as the number of circles occurring in the sample phase sequence between the two choice phase circles. Shorter temporal lags (e.g., 0 and 2 lags) were hypothesized to result in higher interference compared to longer temporal lags (e.g., 4 and 6 lags). The results demonstrated that on trials involving high interference, no differences were found between the two groups. However, healthy older adults significantly outperformed individuals with PD (p<0.05) on trials involving low interference. Although differences were found between the PD and healthy older adult groups, both groups significantly improved on low interference trials compared to high interference trials (p<0.001). The findings indicate that temporal order memory improves in healthy older adults and individuals with PD when interference is reduced. However, individuals with PD demonstrated poorer temporal order memory even with less interference. Therefore, temporal order memory is differentially affected by interference in healthy older adults and individuals with PD. Given that both groups did improve with lessened interference, behavioral interventions that minimize temporal interference potentially could improve memory function in older adults and to a lesser extent in individuals with PD.

Differences in temporal order memory among young, middle-aged, and older adults may depend on the level of interference

Age-related changes in temporal order memory have been well documented in older adults; however, little is known about this ability during middle age. We tested healthy young, middle-aged, and older adults on a previously published visuospatial temporal order memory test involving high and low interference conditions. When interference was low, young and middle-aged adults did not differ, but both groups significantly outperformed older adults. However, when interference was high, significant differences were found among all three age groups. The data provide evidence that temporal order memory may begin to decline in middle age, particularly when temporal interference is high.

The effect of interference on temporal order memory in premanifest and manifest Huntington's disease

BACKGROUND

Frontal-striatal dysfunction has been linked to cognitive impairment in Huntington's disease (HD). The frontal lobes play a role in memory for the temporal order in which items occur in a sequence. However, little is known about temporal order memory in HD or how it may be affected by interference.

OBJECTIVE

The study assessed temporal order memory in patients with manifest HD (n = 20), premanifest gene carriers for HD (Pre-HD; n = 18), and controls (n = 25) using a computerized radial 8-arm maze.

METHODS

On the sample phase of each trial, participants viewed a random sequence of circles appearing one at a time at the end of each arm. On the choice phase, participants viewed two sample phase circles and chose the circle occurring earliest in the sequence. Manipulations of the temporal lag (defined as the number of circles occurring in the sample phase sequence between the two choice phase circles) were conducted to systematically vary interference. Temporally proximal lags were hypothesized to generate more interference relative to temporally distal lags.

RESULTS

The Pre-HD group was significantly impaired (p < 0.05) compared to controls on proximal temporal lags (high interference) but matched controls on distal lags (low interference). HD patients improved as a function of increased lag but demonstrated significant impairments (p < 0.05) across lags relative to controls.

CONCLUSIONS

Temporal order memory is differentially affected by interference during the premanifest and manifest stages of HD. The study identifies a fundamental, yet relatively unexamined, deficit associated with HD.

Visuospatial temporal order memory deficits in older adults with HIV infection

OBJECTIVE

To compare temporal order memory in older adults with and without human immunodeficiency virus (HIV) infection.

BACKGROUND

The frontal and temporal lobes play a key role in temporal order memory for items in a sequence. HIV-associated episodic memory deficits correlate with damage to neocortical interneurons in the fronto-striato-thalamo-cortical pathway and with atypical activation of the medial temporal lobes. Therefore, temporal order memory may be sensitive to neuropathological changes in individuals with HIV.

METHODS

In this study, 50 HIV-seropositive individuals aged ≥ 50 years and 50 seronegative controls performed a computerized visuospatial temporal order memory task. During the sample phase of each trial, participants were shown circles presented 1 at a time in a random sequence at the end of each of the 8 arms of a radial maze. During the choice phase, they were shown the maze with a circle at the ends of 2 of the arms and asked which circle had appeared earlier than the other in the original sequence.

RESULTS

Performance in both groups improved as a function of greater temporal separation between circle presentations. However, the HIV group had significantly worse memory impairment across all temporal separations, and the impairment was independently associated with clinical deficits in executive function and delayed retrospective memory.

CONCLUSIONS

Our results extend prior findings that HIV is associated with deficits in strategic aspects of memory encoding and retrieval. The neural mechanisms warrant further research, as do potential impacts on everyday function, eg, adherence to antiretroviral drug regimens.

Temporal sequence learning in healthy aging and amnestic mild cognitive impairment

BACKGROUND/STUDY CONTEXT: Temporal sequence learning is a critical aspect of episodic memory that may be dependent on the temporal and frontal lobes. Because amnestic mild cognitive impairment (aMCI) and normal aging may result in changes within the temporal and frontal lobes, the present study investigated temporal sequence learning in patients with aMCI, cognitively normal older adults, and young adults.

METHODS

On each trial of a temporal sequence task, circles appeared one at a time at the end of each arm of a computerized radial eight-arm maze. Participants were asked to reproduce the temporal sequence by placing numbered circles (1 to 8) on the arms of the eight-arm maze. Participants were presented with the same fixed sequence on each trial until the sequence was replicated without any errors, or until 15 trials were presented.

RESULTS

Individuals with aMCI required significantly more trials to learn the temporal sequence compared with older adults (p < .05). Older adults required significantly more trials to learn the sequence than young adults (p < .05). Older adults and individuals with aMCI committed significantly more Trial 1 errors (p < .05) than young adults; however, there were no significant differences between the aMCI and older adult groups on Trial 1.

CONCLUSION

The results suggest that temporal sequence learning deficits are detectable in aMCI. These deficits may disrupt a number of cognitive processes, such as episodic memory, that are important for the execution of daily activities. The results suggest that although temporal sequence learning declines with normal aging, this decline is greater in individuals who have a diagnosis of aMCI and are at higher risk for developing Alzheimer's disease.

Executive functions in premanifest Huntington's disease

BACKGROUND

We investigated the viability of psychometrically robust executive function measures as markers for premanifest Huntington's disease (HD).

METHODS

Fifteen premanifest HD subjects and 42 controls were compared on the NIH EXAMINER executive function battery. This battery yields an overall executive composite score, plus working memory, cognitive control, and fluency scores that are measured on psychometrically matched scales. The scores were correlated with two disease markers, disease burden and striatal volumes, in the premanifest HD subjects.

RESULTS

The premanifest HD subjects scored significantly lower on the working memory score. The executive composite positively correlated with striatal volumes, and the working memory score negatively correlated with disease burden. The cognitive control and fluency scores did not differ between the groups or correlate significantly with the disease markers.

CONCLUSIONS

The NIH EXAMINER executive composite and working memory scores are sensitive markers of cognitive dysfunction, striatal volume, and disease burden in premanifest HD.

The importance of considering all attributes of memory in behavioral endophenotyping of mouse models of genetic disease

In order to overcome difficulties in evaluating cognitive function in mouse models of genetic disorders, it is critical to take into account the background strain of the mouse and reported phenotypes in the clinical population being studied. Recent studies have evaluated cognitive function across a number of background strains and found that spatial memory assayed by the water maze and contextual fear conditioning often does not provide optimal results. The logical extension to these results is to emphasize not only spatial, but all attributes or domains of memory function in behavioral phenotyping experiments. A careful evaluation of spatial, temporal, sensory/perceptual, affective, response, executive, proto-linguistic, and social behaviors designed to specifically evaluate the cognitive function each mouse model can be performed in a rapid, relatively high throughput manner. Such results would not only provide a more comprehensive snapshot of brain function in mouse disease models than the more common approach that approaches nonspecific spatial memory tasks to evaluate cognition, but also would better model the disorders being studied.

Effects of number of items and interval length on the acquisition of temporal order discrimination in radial maze in rats

Temporal order discrimination in rats was analyzed using a radial maze. The task consisted of a study phase in which two to five items (arms) were presented sequentially and, after a delay, a test phase in which two of these were simultaneously presented and the rat had to choose the arm presented earlier in the study phase. Acquisition of the task was better as the number of items in the study phase increased when the total study phase length was constant (4 min). Interval length between items in the study phase did not affect the acquisition regardless of the number of items. Additionally, discrimination performance was better when two items with more intervening items in the study phase (temporal lag) were used for the test. However, this tendency was obtained only when the last item of the study phase was included in the test pair. Results suggest that the number of items presented in the sequence, but not interval length between items, is an important factor in temporal order memory, and that a larger number of intervening items, as well as containing the last item in the study phase, contributes to the occurrence of the temporal lag effect.

Poor insight into memory impairment in patients with Huntington disease

BACKGROUND AND PURPOSE

Patients suffering from Huntington disease (HD) have been shown to present with poor self-awareness of a variety of symptoms. The study aimed to assess the self-awareness of memory impairment in HD in comparison to advanced Parkinson disease (PD), mild PD and cervical dystonia.

MATERIAL AND METHODS

Self-awareness was tested in 23 patients with HD by comparing patient and caregiver ratings in reference to clinical control groups (25 patients with advanced PD, 21 with mild PD and 20 with cervical dystonia). Self-awareness was tested using the Self Rating Scale of Memory Functions, which was administered to both the patients and the caregivers. Neuropsychological assessment addressed general cognitive status (Mini-Mental State Examination), verbal learning (Auditory Verbal Learning Test, 15-word list) and mood (Montgomery-Asberg Depression Rating Scale).

RESULTS

Patients with HD significantly underestimated their memory dysfunction. Underestimation of memory deficit correlated with disease duration and disease severity in HD.

CONCLUSIONS

Huntington disease patients underestimate memory dysfunction. These results add to the previous reports on poor insight in HD in other domains and suggest that anosognosia in HD, albeit usually rather mild, may be a generalized phenomenon.

The effect of interference on temporal order memory for random and fixed sequences in nondemented older adults

Two experiments tested the effect of temporal interference on order memory for fixed and random sequences in young adults and nondemented older adults. The results demonstrate that temporal order memory for fixed and random sequences is impaired in nondemented older adults, particularly when temporal interference is high. However, temporal order memory for fixed sequences is comparable between older adults and young adults when temporal interference is minimized. The results suggest that temporal order memory is less efficient and more susceptible to interference in older adults, possibly due to impaired temporal pattern separation.

Comprehensive neurocognitive endophenotyping strategies for mouse models of genetic disorders

There is a need for refinement of the current behavioral phenotyping methods for mouse models of genetic disorders. The current approach is to perform a behavioral screen using standardized tasks to define a broad phenotype of the model. This phenotype is then compared to what is known concerning the disorder being modeled. The weakness inherent in this approach is twofold: First, the tasks that make up these standard behavioral screens do not model specific behaviors associated with a given genetic mutation but rather phenotypes affected in various genetic disorders; secondly, these behavioral tasks are insufficiently sensitive to identify subtle phenotypes. An alternate phenotyping strategy is to determine the core behavioral phenotypes of the genetic disorder being studied and develop behavioral tasks to evaluate specific hypotheses concerning the behavioral consequences of the genetic mutation. This approach emphasizes direct comparisons between the mouse and human that facilitate the development of neurobehavioral biomarkers or quantitative outcome measures for studies of genetic disorders across species.

Impaired postural stability as a marker of premanifest Huntington's disease

Subtle changes in fine motor control have been observed in individuals who carry the Huntington's disease (HD) mutation but have not yet manifested symptoms, referred to as premanifest HD (preHD). However, few studies have examined gross motor impairments in this population. This study sought to examine the role of sensory involvement in maintaining postural stability during the premanifest and manifest stages of HD using computerized dynamic posturography. Eleven HD participants, 22 preHD subdivided into "preHD Near" (<5 years from estimated clinical onset) and "preHD Far" (>5 years from estimated clinical onset), and 17 nongene carriers (NGC) completed a sensory organization test (SOT) to assess postural control when vestibular, visual, and somatosensory information was systematically degraded. The HD group demonstrated greater postural sway than the NGC and preHD Far groups on all conditions including baseline, and greater postural sway than the preHD Near group when sensory information was manipulated. The preHD Near group showed significantly greater postural sway than the preHD Far group when visual and somatosensory information was degraded and only vestibular information was available and reliable for maintaining postural stability. The results of this study highlight subtle postural deficits in the face of changing sensory conditions in preHD up to 5 years before estimated disease onset. The findings suggest that the SOT may be a highly sensitive indicator of early motor impairment and subsequent phenoconversion to manifest HD in preHD.

Temporal ordering deficits in female CGG KI mice heterozygous for the fragile X premutation

The fragile X premutation is a tandem CGG trinucleotide repeat expansion on the FMR1 gene between 55 and 200 repeats in length. A CGG knock-in (CGG KI) mouse with CGG repeat lengths between 70 and 350 has been developed and used to characterize the histopathology and cognitive deficits reported in carriers of the fragile X premutation. Previous studies have shown that CGG KI mice show progressive deficits in processing spatial information. To further characterize cognitive deficits in the fragile X premutation, temporal ordering in CGG knock-in (CGG KI) mice was evaluated. Female CGG KI mice were tested for their ability to remember the temporal order in which two objects were presented. The results demonstrate that at 48 weeks of age, female CGG KI mice with CGG repeat expansions between 150 and 200 CGG repeats performed more poorly on tests of temporal order than wildtype mice, whereas female CGG KI mice with between 80 and 100 CGG repeats performed similarly to wildtype mice. No mice had any difficulty in detecting the presence of a novel object. These data suggest female CGG KI mice show a CGG repeat length-sensitive deficit for temporal ordering.