Effect of clozapine on interval timing and working memory for time in the peak-interval procedure with gaps

Previous research indicates that dopamine controls both the speed of an internal clock [Maricq, A.V., Church, R.M., 1983. The differential effects of haloperidol and methamphetamine on time estimation in the rat. Psychopharmacology 79, 10-15] and sharing of resources between the timer and other cognitive processes [Buhusi, C.V., 2003. Dopaminergic mechanisms of interval timing and attention. In: Meck, W.H. (Ed.), Functional and Neural Mechanisms of Interval Timing. CRC Press, Boca Raton, FL, pp. 317-338]. For example, dopamine agonist methamphetamine increases the speed of an internal clock and resets timing after a gap, while dopamine antagonist haloperidol decreases the speed of an internal clock and stops timing during a gap [Buhusi, C.V., Meck, W.H., 2002. Differential effects of methamphetamine and haloperidol on the control of an internal clock. Behav. Neurosci. 116, 291-297]. Using a 20-s peak-interval procedure with gaps we examined the acute effects of clozapine (2.0mg/kg i.p.), which exerts differential effects on dopamine and serotonin in the cortex and striatum, two brain areas involved in interval timing and working memory. Relative to saline, clozapine injections shifted the response functions leftward both in trials with and without gaps, suggesting that clozapine increased the speed of an internal clock and facilitated the maintenance of the pre-gap interval in working memory. These results suggest that clozapine exerts effects in different brain areas in a manner that allows for the pharmacological separation of clock speed and working memory as a function of peak trials without and with gaps.

A Rorschach Stability Study in a Nonpatient Adult Sample

The objective of this study was to provide new primary data on Rorschach Comprehensive System stability levels. To achieve this, we tested 75 French nonpatient adults twice on the Rorschach with a 3-month interval between the tests. Interrater reliability was in the excellent range for most of the variables studied. The overall stability level in a selected set of previously studied variables was below expectations (median r = .53). Personality, cognitive or self/relational variables yielded higher test-retest correlations than emotional and coping variables. Moderators of stability could be identified: (a) overall level of Task Engagement (TE) in F, m, FM + m, a, FC, Sum C', Sum V, Sum Shd, Fr + rF, INC + FAB, COP, es, Adj es, EGO, and Blends; (b) variations in TE in F, FM, and p; (c) state distress in Zd, m, FM + m, a, C, CF + C, WSumC, FD, and es; (d) variables derived from the number of responses impacted stability in P, Zf, m, FC, CF + C, Sum C', Sum V, MOR, EA, es, and Blends. These results provide further support for the reliability of several measures. Examiner effects as an influence on productivity and TE were identified as an important area for future research.

Embodied temporal perception of emotion

The role of embodiment in the perception of the duration of emotional stimuli was investigated with a temporal bisection task. Previous research has shown that individuals overestimate the duration of emotional, compared with neutral, faces (S. Droit-Volet, S. Brunot, & P. M. Niedenthal, 2004). The authors tested a role for embodiment in this effect. Participants estimated the duration of angry, happy, and neutral faces by comparing them to 2 durations learned during a training phase. Experimental participants held a pen in their mouths so as to inhibit imitation of the faces, whereas control participants could imitate freely. Results revealed that participants overestimated the duration of emotional faces relative to the neutral faces only when imitation was possible. Implications for the role of embodiment in emotional perception are discussed.

Frontal cortex lesions eliminate the clock speed effect of dopaminergic drugs on interval timing

Behavioral and pharmacological challenges using methamphetamine (MAP-0.5 and 1.0 mg/kg, i.p.), haloperidol (HAL-0.12 mg/kg, i.p.), and sulfated cholecystokinin octapeptide (CCK-0.05 and 0.1 mg/kg, i.p.) were used to evaluate the effects of excitotoxic lesions of cholinergic cell bodies in the medial septal area and the nucleus basalis magnocellularis, radiofrequency lesions of the fimbria-fornix, and aspiration lesions of the frontal cortex on interval timing in rats trained on a 40-s peak-interval procedure. Results demonstrated that lesions of the nucleus basalis magnocellularis and frontal cortex selectively reduced the modulatory control of clock speed which is likely mediated by dopamine D(2) receptors located on cortico-striatal neurons.

alpha7 Nicotinic acetylcholine receptors and temporal memory: synergistic effects of combining prenatal choline and nicotine on reinforcement-induced resetting of an interval clock

We previously showed that prenatal choline supplementation could increase the precision of timing and temporal memory and facilitate simultaneous temporal processing in mature and aged rats. In the present study, we investigated the ability of adult rats to selectively control the reinforcement-induced resetting of an internal clock as a function of prenatal drug treatments designed to affect the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR). Male Sprague-Dawley rats were exposed to prenatal choline (CHO), nicotine (NIC), methyllycaconitine (MLA), choline + nicotine (CHO + NIC), choline + nicotine + methyllycaconitine (CHO + NIC + MLA), or a control treatment (CON). Beginning at 4-mo-of-age, rats were trained on a peak-interval timing procedure in which food was available at 10-, 30-, and 90-sec criterion durations. At steady-state performance there were no differences in timing accuracy, precision, or resetting among the CON, MLA, and CHO + NIC + MLA treatments. It was observed that the CHO and NIC treatments produced a small, but significant increase in timing precision, but no change in accuracy or resetting. In contrast, the CHO + NIC prenatal treatment produced a dramatic increase in timing precision and selective control of the resetting mechanism with no change in overall timing accuracy. The synergistic effect of combining prenatal CHO and NIC treatments suggests an organizational change in alpha7 nAChR function that is dependent upon a combination of selective and nonselective nAChR stimulation during early development.

What makes us tick? Functional and neural mechanisms of interval timing

Time is a fundamental dimension of life. It is crucial for decisions about quantity, speed of movement and rate of return, as well as for motor control in walking, speech, playing or appreciating music, and participating in sports. Traditionally, the way in which time is perceived, represented and estimated has been explained using a pacemaker-accumulator model that is not only straightforward, but also surprisingly powerful in explaining behavioural and biological data. However, recent advances have challenged this traditional view. It is now proposed that the brain represents time in a distributed manner and tells the time by detecting the coincidental activation of different neural populations.

Conceptual development and conversational understanding

Children's understanding of the implications of conversation can influence their responses on tasks designed to measure conceptual development. These responses are in keeping with developmental changes in the ability to recognize and resolve ambiguity in communicative contexts, as shown, for example, in children's ability to compute "scalar implicatures". Examining steps children take to overcome difficulties in processing the relevant features of tasks and in correctly interpreting task instructions promise to illuminate mechanisms of conceptual development. We review recent research in this area, focussing on early knowledge of the appearance-reality distinction and knowledge of cosmological concepts.