Analysis of theta power in hippocampal EEG during bar pressing and running behavior in rats during distinct behavioral contexts

Abstract

These experiments examine changes in theta power as measured by wavelet analysis in five rats performing a conditional visual discrimination task and a simple running task. In the conditional task, rats were trained to press one lever to initiate a trial and then to press one of two choice levers, each corresponding to one of two cue lights. Analysis of theta power in this operant task found a large decrease in theta power during the choice bar presses, in contrast to the increase in theta power during trial initiation bar presses. This result seems to stand counter to results that propose consistent relationships between motor actions and theta power (Vanderwolf, EEG Clin Neurophys 26:407-418, 1969), as well as studies suggesting that the lack of bar-press theta is the result of habituation. However, these data can be seen as being in broad agreement with the theoretical framework of sensorimotor integration (Bland and Oddie, Behav Brain Res 127:119-136, 2001). To investigate further the power of theta observed at the termination of type 1 motor activity, a runway task was devised in which rats ran back and forth between two ends of a linear track, one of which was always rewarded and the other never rewarded. Theta power decreased sharply 240 ms before movement ended at the rewarded end, but not at the unrewarded end of the track. These data extend the current scope of theory in demonstrating that hippocampal theta activity can end abruptly 200-400 ms prior to the end of type 1 motor movement when approaching the end of a motor sequence.

Theta oscillations and sensorimotor performance

“…Theta power has been associated with sensorimotor processes (7), and one recent study has shown a dramatic decrease in theta power in the CA1 subfield associated with lever pressing for a reward (34). Figs.…”

Activation of D2 autoreceptors alters cocaine-induced locomotion and slows down local field oscillations in the rat ventral tegmental area

“…We have currently no explanation for this effect which, although significant, was not very marked. This might be due to the fact that theta oscillations are usually associated more with the intention than with the movement itself (Whishaw and Vanderwolf, 1973;Wyble et al, 2004), and that the rise of theta power precedes the onset of voluntary locomotion (Vanderwolf, 1969). We noticed that animals in the saline, cocaine and quinpirole+ cocaine groups exhibit closely spaced successive locomotory episodes.…”

Arc length coding by interference of theta frequency oscillations may underlie context-dependent hippocampal unit data and episodic memory function

“…This could be due to theta rhythm oscillations being shut down when the rat stops at a reward location. The theta rhythm shows reductions at reward locations and decreases even as the rat is approaching a reward location (Wyble et al 2004). The temporary decrease in theta rhythm could result in periodicity being dependent on the latest reward location.…”

“…The temporary decrease in theta rhythm could result in periodicity being dependent on the latest reward location. Note that stopping per se does not have to reset the theta rhythm, as stopping at non-reward locations causes less suppression of theta rhythm (Wyble et al 2004). …”