Deficits in temporal processing correlate with clinical progression in Huntington's disease.

OBJECTIVES: Precise temporal performance is crucial for several complex tasks. Time estimation in the second-to-minutes range-known as interval timing-involves the interaction of the basal ganglia and the prefrontal cortex via dopaminergic-glutamatergic pathways. Patients with Huntington's disease (HD) present deficits in cognitive and motor functions that require fine control of temporal processing. The objective of the present work was to assess temporal cognition through a peak-interval time (PI) production task in patients with HD and its potential correlation with the Unified Huntington's Disease Rating Scale (UHDRS). MATERIALS AND METHODS: Patients with molecular diagnosis of HD and controls matched by age, sex and educational level (n=18/group) were tested for interval timing in short- (3 seconds), medium- (6 seconds) and long (12 seconds)-duration stimuli. RESULTS: Significant differences were observed in the PI task, with worse performance in HD compared to controls. Patients underestimated real time (left-shifted Peak location) for 6- and 12-second intervals (P<.05) and presented decreased temporal precision for all the intervals evaluated (P<.01). Importantly, a significant correlation was found between time performance and the UHDRS (P<.01). Patients' responses also deviated from the scalar property. CONCLUSIONS: Our results contribute to support that timing functions are impaired in HD in correlation with clinical deterioration. Recordings of cognitive performance related to timing could be a potential useful tool to measure the neurodegenerative progression of movement disorder-related pathologies.

Acquisition of response thresholds for timed performance is regulated by a calcium-responsive transcription factor, CaRF.

Interval timing within the seconds-to-minutes range involves the interaction of the prefrontal cortex and basal ganglia via dopaminergic-glutamatergic pathways. Because the secreted protein brain-derived neurotrophic factor (BDNF) is able to modulate dopamine release as well as glutamatergic activity, we hypothesized that BDNF may be important for these timing mechanisms. Recently, the calcium-responsive transcription factor (CaRF) was identified as an important modulator of BDNF expression in the cerebral cortex. In this study, a strain of Carf knockout mice was evaluated for their ability to acquire the 'Start' and 'Stop' response thresholds under sequential and simultaneous training conditions, using multiple (15-second and 45-second) or single (30-second) target durations in the peak-interval procedure. Both Carf(+/-) and Carf(-/-) mice were impaired in their ability to acquire timed response thresholds relative to Carf(+/+) mice. Additionally, control mice given microinjections of BDNF antisense oligodeoxynucleotide to inhibit protein expression in the prefrontal cortex showed timing impairments during acquisition similar to Carf mice. Together, these results suggest that the inhibitory processes required to update response thresholds and exert temporal control of behavior during acquisition may be dependent on CaRF regulation of genes including Bdnf in cortico-striatal circuits.