Haloperidol-based conditioned increase in locomotor activity is disrupted by latent inhibition and extended interstimulus interval

Conditioned catalepsy vs. Increase in locomotor activity induced by haloperidol

Previous research has revealed a high degree of complexity of the conditioned response that appears after associating a context with the effects of the dopaminergic antagonist haloperidol. Specifically, when a drug-free test is performed in the presence of the context, conditioned catalepsy is observed. However, if the test is extended over time, the opposite effect occurs, namely, a conditioned increase in locomotor activity. In this paper, we present the results of an experiment with rats that received repeated administration of haloperidol or saline before or after exposure to the context. Next, a drug-free test was performed to evaluate catalepsy and spontaneous locomotor activity. The results revealed, on the one hand, the expected conditioned response of catalepsy for those animals that received the drug prior to context exposure during conditioning. However, for the same group, an analysis of locomotor activity for an extended period of ten minutes after registering catalepsy revealed an increase in general activity and more faster movements compared to the control groups. These results are interpreted considering the possible temporal dynamics of the conditioned response that could induce changes in dopaminergic transmission responsible for the observed changes in locomotor activity.

BCI Accuracy Using Classifier-Based Latency Estimation and the Optimal Interstimulus Interval

PURPOSE

Detection of event-related potentials (ERPs) in brain-computer interfaces (BCIs) allow for communication by individuals with neuromuscular disorders. Enhancing BCI accuracy may be possible through the exploration of the optimal interstimulus interval (ISI). Our objective is to investigate the relationship between BCI accuracy and the optimal ISI value for an individual.

APPROACH

Using the previously developed classifier-based latency estimation (CBLE) [1], we investigated the relationship between the interstimulus interval (ISI) and P3 Speller BCI accuracy. Participants underwent two consecutive sessions in one day. The first session had a default ISI value of 120ms. An optimal ISI value calculated from the first session was used in the second.

RESULTS

Ten subjects participated in the study. Of the ten, half received an optimal ISI value of 120ms and half 160ms. Accuracy differences after implementing the adjusted ISI ranged from -26.1 percent to 4.35 percent. Suggestions for additional experimental design adjustments are highlighted under the discussion portion of this manuscript.

Temporal Factors Modulate Haloperidol-Induced Conditioned Catalepsy

Repeated pairings of a neutral context and the effects of haloperidol give rise to conditioned catalepsy when the context is subsequently presented in a drug-free test. In order to confirm whether this response is based on Pavlovian processes, we conducted two experiments involving two manipulations that affect conditioning intensity in classical conditioning procedures: time of joint exposure to the conditioned and the unconditioned stimulus, and the length of the inter-stimulus interval (ISI). The results revealed that both an increase in the length of context-drug pairings during conditioning and a reduced ISI between drug administration and context exposure increased conditioned catalepsy. These results are discussed in terms of the temporal peculiarities of those procedures that involve drugs as the unconditioned stimulus along with the role of Pavlovian conditioning in context-dependent catalepsy.