Biomedical subjects

Matthew S Matell

Publications and source records attributed to Matthew S Matell.

7 recordsLinked to original sources

PubMed2006

Impulsive responding on the peak-interval procedure.

The pattern of responding on a peak-interval timing task allows one to make inferences regarding the sources of variation that contribute to interval timing behavior. Non-temporal factors such as impulsivity may impact the validity of these inferences. Rats were trained on a 15s peak-interval procedure (PI) or a mixed 15s behaviorally dependent variable-interval, 15s peak-interval procedure (bdVIPI) for an extended number of sessions. Extended training on the PI revealed a bi-modal distribution in the times at which subjects started responding for temporally predictable reinforcement, suggesting that multiple processes contribute to the behavioral pattern obtained in this procedure. Training on the bdVIPI eliminated the early mode of this bi-modal distribution, thereby decreasing the variation in start times. These results suggest that alternative response options can modulate the influence of impulsivity in timing tasks.

Animals↗

PubMed2006

Single-trials analyses demonstrate that increases in clock speed contribute to the methamphetamine-induced horizontal shifts in peak-interval timing functions.

INTRODUCTION: Drugs that increase dopamine (DA) transmission have been shown to produce an overestimation of time in duration production procedures as exhibited by horizontal leftward shifts of the psychophysical functions. However, the generality of these results has been inconsistent in the literature. MATERIALS AND METHODS: The present report evaluates the effects of five doses of methamphetamine (MAP) (0.5-1.5 mg/kg, i.p.) on two duration production procedures, the single duration peak-interval (PI) procedure and the multiduration tri-peak procedure in rats. RESULTS: We replicated and extended prior results by showing a dose-dependent proportional overestimation of time that was equivalent on both procedures (i.e., subjects behaved as though they expected reinforcement to be available earlier in real time). Single-trials analyses demonstrated that the reduction in peak rate that is often observed after MAP administration is due to an increase in the proportion of trials in which responding occurred at very low rates and without temporal control. However, these low-rate trials were not the source of the leftward shift in the temporal estimates. Rather, we found that the leftward shift of the PI functions was due to proportional changes in the placement of temporally controlled high-rate responding, which is consistent with a DA-mediated alteration in clock speed.

Animals↗

PubMed2005

Dopamine D1 activation shortens the duration of phases in stereotyped grooming sequences.

Rats frequently emit grooming actions in a highly stereotyped, syntactic chain in which three distinct phases of facially directed forearm movements are sequentially emitted in a rule-governed pattern and followed by body-directed licking. The present study evaluated the effects of the full dopamine D1 agonist, SKF 81297, and the partial dopamine D1 agonist, SKF 38393, on the duration of individual phases of stereotyped grooming chains. We found that systemic administration of SKF 81297 significantly shortened grooming chain duration. An examination of the fine temporal structure of syntactic grooming chain actions showed that duration changes were correlated with decreased numbers of actions in phases I and IV of the chain. Phases II and III were not changed in duration, although there were some structural distortions introduced. The partial D1 agonist, SKF 38393, had no effect on duration or number of component actions in the grooming chain. Based on these results, we hypothesize that the timing of syntactic grooming phase transitions may involve a D1-mediated internal clock process that is altered by full D1 agonist activation. By this model, SKF 81297 increases the speed of the clock used for the temporal control of grooming actions, and thus shortens phase durations.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2004

Cortico-striatal circuits and interval timing: coincidence detection of oscillatory processes.

Humans and other animals demonstrate the ability to perceive and respond to temporally relevant information with characteristic behavioral properties. For example, the response time distributions in peak-interval timing tasks are well described by Gaussian functions, and superimpose when scaled by the criterion duration. This superimposition has been referred to as the scalar property and results from the fact that the standard deviation of a temporal estimate is proportional to the duration being timed. Various psychological models have been proposed to account for such responding. These models vary in their success in predicting the temporal control of behavior as well as in the neurobiological feasibility of the mechanisms they postulate. A review of the major interval timing models reveals that no current model is successful on both counts. The neurobiological properties of the basal ganglia, an area known to be necessary for interval timing and motor control, suggests that this set of structures act as a coincidence detector of cortical and thalamic input. The hypothesized functioning of the basal ganglia is similar to the mechanisms proposed in the beat frequency timing model [R.C. Miall, Neural Computation 1 (1989) 359-371], leading to a reevaluation of its capabilities in terms of behavioral prediction. By implementing a probabilistic firing rule, a dynamic response threshold, and adding variance to a number of its components, simulations of the striatal beat frequency model were able to produce output that is functionally equivalent to the expected behavioral response form of peak-interval timing procedures.

Animals↗

PubMed2004

Differential modulation of clock speed by the administration of intermittent versus continuous cocaine.

The roles that psychostimulant sensitization and tolerance play in temporal perception in the seconds-to-minutes range were assessed in rats. Cocaine (20 mg/kg/day) was administered for 2 weeks either intermittently via daily injections (induces sensitization) or continuously via an osmotic minipump (induces tolerance). Interval timing was evaluated throughout administration and withdrawal. Injections of cocaine caused immediate, proportional, leftward shifts in peak times, indicating an increase in the speed of an internal clock. These shifts grew progressively larger with repeated administration, indicating that stimulant-induced increases in clock speed can be sensitized. Continuous cocaine administration produced no reliable effects. These results suggest that the mechanisms of sensitization may play a considerable role in drug-induced alterations of the perception of time.

Animals↗

PubMed2003

Interval timing and the encoding of signal duration by ensembles of cortical and striatal neurons.

This study investigated the firing patterns of striatal and cortical neurons in rats in a temporal generalization task. Striatal and cortical ensembles were recorded in rats trained to lever press at 2 possible criterion durations (10 s or 40 s from tone onset). Twenty-two percent of striatal and 15% of cortical cells had temporally specific modulations in their firing rate, firing at a significantly different rate around 10 s compared with 40 s. On 80% of trials, a post hoc analysis of the trial-by-trial consistency of the firing rates of an ensemble of neurons predicted whether a spike train came from a time window around 10 s versus around 40 s. Results suggest that striatal and cortical neurons encode specific durations in their firing rate and thereby serve as components of a neural circuit used to represent duration.

Animals↗

PubMedDate not supplied

Not "just" a coincidence: frontal-striatal interactions in working memory and interval timing.

The frontal cortex and basal ganglia play central roles in working memory and in the ability to time brief intervals. We outline recent theoretical and empirical work to suggest that working memory and interval timing rely not only on the same anatomic structures, but also on the same neural representation of a specific stimulus. Specifically, cortical neurons may fire in an oscillatory fashion to form representations of stimuli, and the striatum (a basal ganglia structure) may detect those patterns of cortical firing that occur co-incident to important events. Information about stimulus identity can be extracted from which cortical neurons are involved in the representation, and information about duration can be extracted from their relative phase. The principles derived from these biologically based models also fit well with a family of behaviourally based models that emphasise the importance of time in many working memory phenomena.

Basal Ganglia↗