Selective adjustment of the speed of internal clock and memory processes.

Abstract

Four experiments studied the scaling of time by rats. The purpose was to determine if internal clock and memory processes could be selectively adjusted by pharmacological manipulations. All of the experiments used a temporal discrimination procedure in which one response ("short") was reinforced following a 2-sec noise signal and a different response ("long") was reinforced following an 8-sec noise signal; unreinforced signals of intermediate duration were also presented. The proportion of "long" responses increased as a function of signal duration. All drugs were administered intraperitoneally (ip) and their effect on clock or memory processes was inferred from the observed pattern of change in the point of subjective equality of the psychophysical functions under training and testing conditions. Experiment 1 demonstrated that methamphetamine (1.5 mg/kg) can selectively increase clock speed and that haloperidol (.12 mg/kg) can selectively decrease clock speed. Experiment 2 demonstrated that footshock stress (.2 mA) can selectively increase clock speed during continuous administration but leads to a decrease in clock speed below control values when the footshock is abruptly terminated. Experiment 3 demonstrated that vasopressin (.07 pressor units/kg) and oxytocin (.02 pressor units/kg) can selectively decrease the remembered durations of reinforced times, which suggests that memory storage speed increased. Experiment 4 demonstrated that physostigmine (.01 mg/kg) can selectively decrease the remembered durations of reinforced times and that atropine (.05 mg/kg) can selectively increase these remembered durations, which suggests that memory storage speed was differentially affected. The conclusion is that internal clock and memory processes can be dissociated by selectively adjusting their speed of operation and that these changes can be quantitatively modeled by a scalar timing theory.

Effects of aging on absolute identification of duration.

“…Lesioning of the frontal cortex in rats leads to a shift in response gradients that suggests that reference durations are remembered as too long, and choline antagonists have a similar (though reversible) effect (Meck, 1983(Meck, , 1994Meck & Church, 1987;Meck et al, 1986). The choline system is known to be affected by aging (Bartus, Dean, Beer, & Lippa, 1982;Bartus et al, 1987).…”

Nucleus basalis magnocellularis and medial septal area lesions differentially impair temporal memory

“…As detailed elsewhere (Meek, 1983(Meek, , 1986Church, 1984;Church and Meek, 1987;Meek and Church, 1987a, b), manipulations that affect the internal clock result in an immediate shift of peak time that is gradually corrected and returned to normal with experience. In contrast, alterations of memory storage produce the pattern observed here: little or no immediate effect after treatment, and a gradual development of a relatively permanent shift in peak time.…”

The Effect of Mindfulness Meditation on Time Perception

“…An increase in arousal is most often associated with an increase in pacemaker speed, and this, in turn, increases the number of pulses accumulated within a given time period and produces an overestimation. However, this increase in pacemaker speed would produce a multiplicative effect, i.e., an increase in the magnitude of the time distortion as the length of stimulus durations increased (Maricq et al, 1981;Meck, 1983). In order to test this hypothesis, we compared the average d' of the shortest comparison durations (400, 600, and 800ms) with the average d' of the longest comparison durations (1200, 1400, and 1600ms), with an arousal account predicting an increase in d' for longer durations (Gil, Niedenthal, & Droit-Volet, 2007).…”

“…Time estimation is based on the number of pulses accumulated, with more pulses leading to an increase in perceived duration. Arousal produces an overestimation of time due to an increase in the pacemaker's speed (Maricq, Roberts, & Church, 1981;Meck, 1983;Wearden & Penton-Voak, 1995; although see Lui, Penney, & Schirmer, 2011). In contrast, if attention to the task distracts from the processing of temporal information, this opens the switch and some pulses are lost.…”