Timing and hippocampal theta in animals

All animals have at least two different internal clocks, one governing cognition of time of day, and the other concerning awareness of seconds and minutes. In the latter case, organisms show scalar properties. The timing mechanisms in the brain may function similarly throughout the animal kingdom, but this is not yet clear. Previous studies have shown that the hippocampus is intricately involved with the process of interval timing. Data concerning electrophysiological field potentials in the hippocampus show obviously rhythmic activity, known as hippocampal theta activity. An information-processing model of interval timing postulates three distinct stages: a clock, a memory, and a decision stage /11/. The timing process includes memory processing, which means that the hippocampus works together with working memory to estimate current time passing

A behavioral approach to the preference on numbers

559 undergraduates answered one number using the numbers 0-9 without special instructions. Histograms of each response were analyzed using a log-liner model and chi-square methods. Distribution biases were studied with the choice of preference number. The first preference distribution of numbers showed that the most frequent number was three. Five and seven were also chosen frequently. The least frequent number was nine. All characteristic numbers in appearance were odd and almost chance level frequency were even without zero. This phenomenon was very steady state in undergraduates. The reason of this phenomenon was collected from subjects. The most frequent answer of reasons was position preference of sequence numbers. A pseudo scientific conviction might be shaped from the information of communication. It was so called superstitious behavior. In human subjects random response number was rare generated. An instruction for the prediction of the least number in next response forced the preference changing. This result showed the distribution of numbers were near chance level frequency. It suggests that the human being might have the tendency of straight response bias

Successive measurement of blood pressure during temporal discrimination task in rats

Rats were trained to discriminate 8 seconds duration under a differential reinforcement of long latencies (DRLL) schedule. Once the discrimination was learned, rats were implanted with an indwelling vascular catheter in femoral artery. A femoral arterial catheter (PE20 heat-fused to PE10) was inserted into a rat for measurement of blood pressure. The catheter was routed subcutaneously to exit at the back of the neck and connected to syringe with extension tubing (PE50 heat-fused to PE20). The vascular catheter was flushed with saline containing heparin, and the rats were placed in individual Plexiglas home cages. After recovery of surgery, blood pressure and response latencies were recorded on a DRLL8' schedule in a operant chamber. Arterial pressure was slightly changed with the time stages on a DRLL8' schedule. Arterial pressure was elevated for the end of a eight seconds trial. The results showed that temporal discrimination correlated with internal cardiovascular changes. The femoral artery catheterization procedure is preferable in terms of simultaneously recording of blood pressure and response latencies

The Effects of Minimum Rewards’ Experience Order in Rats Gambling Task

Gambling-like activities are more familiar than traditional gambling in everyday life. Games such as gacha, fukubukuro, and social online games have been linked to problematic behaviors that are similar to those seem in pathological gamblers. However, it is difficult to distinguish gambling from gambling-like activities. In this study, we examined one of the most remarkable differences, which is the existence of minimum rewards, i.e., rewards in “lost trials.” We trained four male Long-Evans Rats to make a choice between a fixed-reward and a variable-reward in a 2-lever Skinner box. According to whether the rat won or lost the trial, selecting a variable-reward resulted in a stimulus that predicted 0 or 4 food pellets in the gambling sessions (GB), and choosing a variable-reward in the gambling-like sessions (semiGB) resulted in a different stimulus that predicted 1 or 3 food pellets. The mean amount of reinforcer was same between fixed-reward choice and variable-reward choice. However, we found that rats with previous GB experience (GB-semiGB) had higher response rates for the variable-reward choice. In contrast, those without previous GB experience (semiGB-GB) did not show higher response rates in the GB sessions

The effects of the appearance rate of stimulus on the rats' auditory evoked potentials

The mismatch negativity (MMN) is a component of the auditory event-related brain potential which is elicited by the infrequent stimuli within the repeated frequent stimuli. The stimulus sequence which generates the MMN has the property which elicit following two automatic processes: (1) the neural model for frequent stimulus is established, and difference between incoming stimulus and the model is detected (Cowan, Winkler, Teder, & Naatanen, 1993) and/or (2) the neural model for the context, infrequent as figure and frequent as ground, is established, and the attention to figure is called. The Papez circuit is known to be critical for memory because the demage of these regions cause the memory deficit. In this study, auditory evoked potentials for frequent and infrequent tones in the above stimulus sequence were recorded from the regions of the Papez circuit (dentate gyrus, mammillary body, anterior thalamus) and cortices (auditory and entorhinal). The purpose of this study is to examine following three : (1) whether the components which correspond to the automatic processes appear or not in the regions of the Papez circuit; and if these components appear, (2) the temporal relation between the information processing in the Papez circuit and that in cortical area by comparing the latencies of processing in the Papez circuit and that in cortical area by comparing the latencies of components; (3) the effects of stimulus appearance rate on those components in the Papez circuit. In the regions of the Papez circuit, the amplitudes of the positive component peaking at about 30 and 70msec for infrequent tones were higher than those for frequent tones. But in the cortical area, only the amplitude of positive component peaking at about 70msec for infrequent tones was higher than those for frequent tones. These phenomenon disappeared as frequent and infrequent tones came to be more equal in the stimulus appearance rate. The results suggested that the information processing which based on the neural model of the frequent standard stimulus and/or on the context of global stimulus sequence occurred in the cortical area and the Papez circuit in parallel

Use of cue stimulus during temporal discrimination in rats.

A series of experiments examined the observing responses as the usage of a cue stiumlus during temporal discrimination learning. The observing response was defined as pressing a lever which presented a cue stimulus but not contingent reinforcers. Five food deprived rats were examined using differential reinforcement of long latencies (DRLL) schedule with a two levers operant chamber. In the first procedure which was presented flicker stimuli automatically, acquired reinforcement effectively. The results showed that flicker stimulus became cue stimulus. The second procedure required a observing response to present a cue stimulus. However, boserving response appeared little numbers. Next, we used more difficult procedures than the secong one. These schedules have long DRLL value. In such schedules, the number of observing responses were more than that in easy schedule

Relationship between choice of timing process and temporal information memory in rats

The effect of the interruption of the timing stimulus (gap) in rats was examined by using the durationdiscrimination task. Rats trained to discriminate the duration of light stimulus (2 or 8s), then breaks of stimulus(0.5, 1, 2, 4, 8s) were inserted. They may restart the entire timing process called “reset" or they may “stop"timing for the duration of the gap. The reset had selected by the expansion of the gap duration. The selection rateof the stop increased in the processing at the gap after having trained the temporal information maintenancetask. These results suggested that the choice of timing processes, reset or stop, depend on the memory of thetemporal information

Preliminary Study of Direction Discrimination Task Using Motion Lines in Rats

Motion lines (MLs) are an effective technic for illustrating dynamic events such as fast movement of an object in a still picture. This study explored whether MLs have the same effect for human and animals. First, we had a task to discriminate the motion direction of circles using touchscreen method in rats. After rats showed high performance of direction discrimination, we tested with MLs probe stimulus. Only one rat showed good results in direction discrimination; however, its performance in MLs probe showed chance level. Second, we trained another group of rats to discriminate the direction of MLs stimulus. Two rats achieved learning criterion in MLs direction discrimination. Then we tested the probe of moving directions, the results showed only chance level performance. These results of this study suggest that we should conduct discrimination task with easily stimulus

Behavioral study of time perception with nigrostriatal lesion in rats. <Articles>

We studied the effects of an injection of 6-hydroxydopamine (6-OHDA) into the substantianigra of rats on the performance of timing behavior by using a peak interval (PI) procedure. Rats were trained on a PI 30-s procedure for 30 sessions. Then, subjects were divided into three groups: lesion (n=6), operational sham lesion (n=3) and intact (n=3). After 6-OHDA treatment, subjects were retrained on the PI 30-s procedure for 15 sessions and were checked for their timing behavior. Results indicated that sham and intact groups did not change the performance of timing between pre- and post- operation treatment. In the lesion group, a behavioral change occurred shortly after lesion treatment. They showed a dull curved peak in PI 30-s and peak time showed an in accuracy of 30-s. However, the lesion group recovered their performance following repeated training for 15 sessions. It is suggested that we should further investigate the durability of the 6-OHDA, as well as conduct histological analysis of the striatum, which is the dopamine (DA) projection ahead of the substantianigra. Such investigations would enable the identification of possible relationships between the function of substantianigra and time perception

Study of Response Latencies of Interval Bisection Task in Rats

Interval timing, whose range is from a second to several minutes among the sense with respect to time, is related with feeding behavior, decision making and time estimation of animals. In this study, we used interval bisection task, which is a method for examining this interval timing quantitatively. First, rats learned left and right lever pressing associated with the tone stimuli of 2 seconds and 8 seconds for each. Second, probe stimulus tones (e. g. 2.5, 3.2, 4, 5, 6.4 seconds) were presented, and we observed which lever rats selected. When the proportion of the lever pressing associated with the 8 seconds tone is 50%, the point of subjective equality (PSE) can be obtained. The PSE is an indicator of decision making in time perception. In order to investigate whether the difference in the physical properties of the stimulus affects the time perception, we used two kinds of tones, a continuous tone and a 4 Hz pulse tone. The results suggest that the difference in physical properties between continuous tone and 4 Hz pulse tone does not affect time perception. As another index, response latency of lever pressing for each tone presented in the task was calculated. As a result, at the testing stage, a peak in a distribution of response latency was around 3.2 seconds or 4 seconds of probe stimulus. The durations of the peak was similar to PSE. From these results, it was suggested that response latency is an important indicator in decision making of which lever selected