Decline in hippocampal theta activity during cessation of locomotor approach sequences: amplitude leads frequency and relates to instrumental behavior.

Hippocampal theta frequency and amplitude decrease as locomotor approach slows and the goal is reached. This study compared the declines of these theta parameters and related them to behavioral events. Theta activity was recorded with bipolar electrodes spanning cornu Ammon, sector 1 or cornu Ammon, sectors 2/3 cell layers of the dorsal hippocampus in 12 rats trained to approach and depress a treadle which exposed a milk dipper.

Hippocampal theta activity and behavioral sequences in a reward-directed approach locomotor task.

Hippocampal rhythmic slow wave activity (theta) has been implicated in the processing of stimuli associated with movement. This study determined whether the theta rhythm showed phase relationships or changes in amplitude and frequency with the onset of stimuli and behavioral sequences in a skilled locomotor approach task. Rats with bipolar electrodes spanning CA1 approached a stall, turned to enter it, approached and depressed a treadle, waited 1.

Hippocampal theta activity related to elicitation and inhibition of approach locomotion.

This study determined if the hippocampal theta rhythm showed phase relationships or changes in amplitude and frequency with the onset of stimuli and locomotion in a task in which auditory cues initiated and suppressed approach locomotion. Rats with electrodes in the dorsal hippocampus lapped at a milk dipper and were presented a tone which predicted the delivery of a food pellet. In some trials the pellet cue tone was negated by 60-Hz clicks beginning 0.

Brainstem regions with neuronal activity patterns correlated with priming of locomotor stepping in the anesthetized rat.

Locomotor stimulation in the perifornical hypothalamus produces a transient facilitation of subsequent locomotion, a priming effect, such that stepping to a second train of stimulation occurs with a shorter latency of onset and increased amplitude. Neurons responsible for the initiation of this facilitated stepping presumably respond to locomotor stimulation with a similar priming effect, i.e.

Priming pattern determines the correlation between hippocampal theta activity and locomotor stepping elicited by stimulation in anesthetized rats.

The after-effects of locomotor stimulation are a transient facilitation of locomotor initiation (the priming effect), and a transient increase in hippocampal rhythmic slow activity in the 3-6 Hz band of the theta range. The similar time course of the two effects suggests that hippocampal 3-6 Hz activity may be linked to the excitability of locomotor initiation. This study tested the hypothesis that power in the 3-6 Hz band that is present prior to stimulation would predict the magnitude of elicited stepping.

Hippocampal theta activity and facilitated locomotor stepping produced by GABA injections in the midbrain raphe region.

Inactivation of neurons in the midbrain raphe region produces increases in locomotor activity, and it appears that they function to suppress locomotion. Inactivation of neurons there also produces hippocampal slow wave (theta) activity and it appears that they also function to inhibit rhythmic activity in the hippocampus. We determined whether the degree of association between the two effects was consistent with the operation of a single mechanism.

Locomotion and head scanning initiated by hypothalamic stimulation are inversely related.

Stimulation in the hypothalamus elicits locomotor stepping. Before stepping is initiated, head scanning movements occur. We determined the relationships between the latency of locomotor initiation and the number, extent and direction of the head scanning movements.

Coordination of neck and hindlimb extension during the initiation of locomotion elicited by hypothalamic stimulation.

We tested the hypothesis that during the initiation of stepping elicited by hypothalamic stimulation, hindlimb extension was coordinated with head extension in the sagittal plane. Chronic stimulation electrodes (monopolar stainless-steel, 125 microm diameter) were implanted bilaterally into the perifornical hypothalamus of anaesthetized rats (N = 15) under stereotaxic control. Under freely moving and awake conditions, 18 sites which reliably elicited forward locomotion at a latency of approximately 3 s were tested in a videotaping session.

GABA injected into the anterior dorsal tegmentum (ADT) of the midbrain blocks stepping initiated by stimulation of the hypothalamus.

Previous work showed that the activity rates of certain neurons in the anterior dorsal tegmentum (ADT) of the midbrain correlated with the onset of stepping elicited by hypothalamic stimulation. This study determined if reversible inactivation of the ADT would block locomotion elicited by hypothalamic stimulation of anesthetized rats (urethane, 800 mg/kg). GABA (concentrations 0.

Priming of locomotor initiation by electrical stimulation in the hypothalamus and preoptic region in the anesthetized rat.

Electrical stimulation at a locomotor site can prime (i.e., shorten the latency to initiate) stepping elicited by subsequent stimulation of the same or a different site.

Neural activity in the midbrain correlated with hindlimb extension initiated by locomotor stimulation of the hypothalamus of the anesthetized rat.

Midbrain neuronal activity that correlated with the initiation of locomotion produced by hypothalamic stimulation was studied. Locomotion was elicited by electrical stimulation in the perifornical hypothalamus of 59 rats anesthetized with Nembutal. The first hindlimb extension indexed stepping onset.

Preoptic and hypothalamic neurons and the initiation of locomotion in the anesthetized rat.

Despite its insensate condition and apparent motoric depression, the anesthetized rat can provide useful information about the systems involved in locomotor initiation. The preparation appears to be particularly appropriate for the study of the appetitive locomotor systems and may be more limited for the study of the circuits involved in exploratory and defensive locomotion. In the anesthetized rat, pharmacological evidence indicates that the preoptic basal forebrain contains neurons which initiate locomotor stepping.

Double dissociation of spatial and object visual memory: evidence from selective interference in intact human subjects.

A functional dissociation of the spatial and object visual systems was produced by selective interference in intact young adults. Subjects were instructed to remember the location of a dot in a spatial memory test, and the form of an object memory test. As predicted by current notions of dissociable visual systems in the primate, spatial memory was selectively impaired by a movement discrimination spatial task, whereas object memory was selectively impaired by a color discrimination object task.

Microstimulation mapping of the basal forebrain in the anesthetized rat: the "preoptic locomotor region".

Previous studies have indicated that the basal forebrain at the level of the preoptic area contains neurons which participate in the initiation of locomotion. This study attempted to localize those neurons by mapping sites at which 25- and 50-microA stimulation (50 Hz, 0.5 ms cathodal pulses, 10-s trains) initiated hindlimb stepping.

Locomotor sites mapped with low current stimulation in intact and kainic acid damaged hypothalamus of anesthetized rats.

To determine whether local neurons mediated the locomotor effects of electrical stimulation of the lateral hypothalamus, kainic acid injections (0.5-1.25 micrograms), intended to destroy neural somata as opposed to fibers of passage, were made unilaterally in the tuberal-posterior hypothalamus of 22 rats.

Locomotor stepping initiated by glutamate injections into the hypothalamus of the anesthetized rat.

Glutamate (50 mM, 50 nl) injected into the tuberal and posterior hypothalamus was tested for capacity to elicit locomotor stepping. Rats (n = 23) were anesthetized with Nembutal and suspended by a sling in a stereotaxic apparatus such that locomotor stepping rotated a wheel. In 61 of 275 sites tested, stepping was initiated by glutamate injections within 60 s.

Locomotor stepping elicited by electrical stimulation of the hypothalamus persists after lesion of descending fibers of passage.

Locomotion initiated by electrical stimulation of the lateral hypothalamus could be due to activation of local neurons or of fibers of passage descending from locomotor regions in the basal forebrain. This study mapped hypothalamic sites for electrically elicited locomotion in six rats with electrolytic lesions of the ipsilateral basal forebrain sources of descending fibers of passage. For mapping, anesthetized rats were held in a stereotaxic apparatus supported by a sling so that stepping movements rotated a wheel.

Latency to initiate locomotion elicited by stimulation of the diencephalon positively correlates in awake and anesthetized rats.

Locomotor stepping can be elicited by brain stimulation at various diencephalic sites under moderate levels of Nembutal. This study determined if locomotor initiation measured under anesthesia provides a valid measure of the intersite factors which determine initiation in the awake condition. We compared the latencies to initiate locomotor stepping elicited by electrical stimulation (50 microA, 0.

Initiation and execution of locomotion elicited by diencephalic stimulation: regional differences in response to nembutal.

At moderate levels of Nembutal, within the anesthetic range, locomotor stepping can be elicited by brain stimulation. We determined if Nembutal (7, 14 and 28 mg/kg) had different effects on locomotion elicited by stimulation at different brain regions. Two regions were compared: the medial forebrain bundle (MFB, 13 sites) and the areas medial and dorsal to it (MED/DORSAL, 20 sites).

Midbrain areas required for locomotion initiated by electrical stimulation of the lateral hypothalamus in the anesthetized rat.

Locomotor stepping in the Nembutal-anesthetized rat was elicited by electrical stimulation of either of two sites in the right or left posterolateral hypothalamus. Essential midbrain loci were identified by reversibly blocking the elicited locomotion through local injections of the anesthetic procaine (15%, 0.5 microliter).

Unilateral and bilateral lesions of the anteromedial cortex increase perseverative head movements of the rat.

Lesions of the anteromedial cortex were made in rats trained to orient their heads to 9 positions located laterally and centrally in upper, middle and lower regions of space. The water-deprived subjects were tested in sessions of 20 trials in each of which all positions were baited once with a small amount of water. Training continued until no position was consistently missed and the number of returns to positions already selected on that trial (perseverative responses) was low and stable.

Lateral neglect in a head movement task: more impairment with unilateral than bilateral lesions of the superior colliculus in the rat.

Unilateral lesions of the superior colliculus produce contralateral neglect. This study determined if bilateral lesions would impair head orientation in a way expected from the summation of two contralateral neglects. Rats were trained to make various head movements to get water at a 3 x 3 array of holes, each with a recessed water-baited dipper.

Midbrain stimulation in the anesthetized rat: direct locomotor effects and modulation of locomotion produced by hypothalamic stimulation.

The midbrain contains circuits that modulate locomotion. To delineate some of the involved regions, low-level stimulation (25 microA, 10 s train of 0.5 ms pulses at 50 Hz) was applied to the midbrain during locomotor stepping.

Locomotion elicited by lateral hypothalamic stimulation in the anesthetized rat does not require the dorsal midbrain.

Locomotor stepping elicited by lateral hypothalamic stimulation in the anesthetized rat is blocked by lesions in the anterior ventromedial midbrain. This study determined in acute experiments whether the dorsal midbrain regions implicated in locomotion were also part of the necessary pathway. Rats were anesthetized with Nembutal and held in a stereotaxic apparatus so that stepping responses rotated a wheel.