Neuronal responses in monkey anterior putamen during operant bar-press behavior

Single neuron activity was recorded in the monkey anterior putamen to compare visuomotor-related responses during operant bar-press behavior with visual discrimination of objects. Of 615 neurons recorded 9.8% ( ) responded to the presentation of food during forced delay of access to the bar. Of these 60 neurons, 38 were also tested with nonfood, and 19 of these responded to the nonfood objects regardless of the following movement. The amplitude of the visual-related responses of some differential neurons was graded for different objects to reflect the relative degree of preference for the food presented. However, these responses disappeared in reaction time tasks in which the bar could be accessed for pressing immediately upon presentation of an object. The visual response latency of differential neurons ranged from 50 to 700 ms (mean ± SD, 386 ±211 ms), which was longer than that of the nondifferential responses (207 ± 204 ms). These results suggest that anterior putamen neurons might participate in estimation of visual information that could be related to forecasting movement.     

Influence of acetylcholine on neuronal activity of monkey amygdala during bar press feeding behavior

Single neuron activity in the monkey amygdala was investigated during cue signalled conditioned bar press feeding behavior and the effects of electrophoretically applied acetylcholine (ACh) and atropine were analyzed. ACh increased the firing rate of one third of the neurons tested; these excitatory responses were inhibited by the muscarinic receptor antagonist atropine. No characteristic location of ACh-sensitive neurons was found, cells were diffusely distributed throughout the amygdala. Activity of ACh-sensitive neurons did not correlate with any particular event during the bar press feeding task. However, continuous application of ACh at low current intensity during the task significantly enhanced the task-related excitatory firing patterns, or markedly attenuated the inhibitory responses. Continuous application of atropine elicited or enhanced inhibitory response patterns. These results suggest that the cholinergic system of the monkey amygdala facilitates neuronal excitation but attenuates inhibition related to various phases of feeding behavior, such as to cue recognition, food aquisition and rewarding process.     

Feeding-related activity of glucose-and morphine-sensitive neurons in the monkey amygdala

Feeding-related neuronal activity of monkey amygdalar glucose-sensitive and morphine-sensitive cells was investigated during a task that required bar-pressing to obtain food. Both glucose-sensitive and morphine-sensitive cells, located mostly in the centromedial part of the amygdala, decreased firing during the bar-press period more often than insensitive cells. Naloxone attenuated the decrease in activity during the bar press period. The results suggest involvement of these glucose- and morphine-sensitive cells in the control of food acquisition behavior.     

Visual responses related to food discrimination in monkey lateral hypothalamus during operant feeding behavior

Single neuron activity was recorded from monkey lateral hypothalamic area (LHA) to relate neuronal events to food discrimination and initiation of procurement movement in operant bar press feeding behavior. Of 429 neurons tested, 68 (16%) responded during visual phase. Of these, 30 (7%) responded selectively to the sight of food or non-food associated with a juice reward, but not to the sight of meaningless non-food or food associated with aversive saline. Neuronal activity related to discrimination was readily influenced by extinction, reversal or satiation. The strength of visual responses was correlated with latency of bar press initiation and speed of bar pressing, but was not related directly to bar press movement. These suggest that the LHA is deeply involved in discrimination of reinforcement or non-reinforcement, and might be associated with higher functions to regulate internal states such as physiological need to get food during operant feeding behavior.     

Opiate mechanism in reward-related neuronal responses during operant feeding behavior of the monkey

Reward-related neuronal activity and its modulation by morphine and naloxone was investigated by extracellular single neuron recording and electrophoretic application of drugs in the lateral hypothalamus, during operant feeding of the monkey. Morphine-sensitive neurons responded more often during bar press and ingestion-reward phases. Naloxone blocked only ingestion-reward responses, especially the inhibitory ones. The results suggest that the central opiate system can be involved in reward-related neuronal responses in the lateral hypothalamic area of the monkey.     

Visually induced signal-locked neuronal activity changes in precentral motor areas of the monkey: hierarchical progression of signal processing

In the precuing paradigm, two successive visual signals were presented to trained monkeys. The first one, the preparatory signal, provided complete, partial or no prior information about parameters, such as direction and extent of the forthcoming wrist movement. After a delay, the illumination of a second visual signal, the response signal, called for execution of the movement and indicated the target. Signal-locked neuronal activity changes, i.e. those which occured time-locked to the signal onset, were recorded in the premotor cortex and the primary motor cortex of the monkey and classified as selective or non-selective. Selective neurons were defined as those responding to particular information, for instance information about movement direction, provided by the signal, while non-selective neurons responded to all signals irrespective of any contained information. Clear latency differences according to both the selectivity of the neuronal response and the area in which the neuron was recorded could be discerned. The mean latency of non-selective activity changes was significantly shorter than that of selective activity changes. Furthermore, the mean latency of premotor cortical responses was significantly shorter than that of primary motor cortical responses. The data indicate the existence of distinct levels of signal processing from the very general to the highly specific.     

The presence of an audience modulates responses to familiar call stimuli in the male zebra finch forebrain

The ability to recognize familiar individuals is crucial for establishing social relationships. The zebra finch, a highly social songbird species that forms lifelong pair bonds, uses a vocalization, the distance call, to identify its mate. However, in males, this ability depends on social conditions, requiring the presence of an audience. To evaluate whether the presence of bystanders modulates the auditory processing underlying recognition abilities, we assessed, by using a lightweight telemetry system, whether electrophysiological responses driven by familiar and unfamiliar female calls in a high‐level auditory area [the caudomedial nidopallium (NCM)] were modulated by the presence of conspecific males. Males had experienced the call of their mate for several months and the call of a familiar female for several days. When they were exposed to female calls in the presence of two male conspecifics, NCM neurons showed greater responses to the playback of familiar female calls, including the mate's call, than to unfamiliar ones. In contrast, no such discrimination was observed in males when they were alone or when call‐evoked responses were collected under anaesthesia. Together, these results suggest that NCM neuronal activity is profoundly influenced by social conditions, providing new evidence that the properties of NCM neurons are not simply determined by the acoustic structure of auditory stimuli. They also show that neurons in the NCM form part of a network that can be shaped by experience and that probably plays an important role in the emergence of communication sound recognition.     

Potential related to no-go reaction in go/no-go hand movement with discrimination between tone stimuli of different frequencies in the monkey

Monkeys were trained for go/no-go reaction-time hand movement with discrimination between tone stimuli of different frequencies, and field potentials related to the discriminative movement were recorded with electrodes implanted in various cortical areas and analysed by averaging procedure. In the cortex of the dorsal bank of the principal sulcus, surface-negative, depth-positive (s-N, d-P) potentials were recorded specifically on the no-go trial. The same monkey was also examined for go/no-go reaction-time hand movement with color discrimination. In the same monkey, the potentials related to the no-go reaction on the auditory stimulus were recorded in the rostral part of the dorsal bank of the principal sulcus, whereas the s-N, d-P potentials on the no-go visual stimulus were observed in the caudal part of the same bank. It is suggested that the dorsal bank of the principal sulcus is essentially related to the integrative functions such as judgement not to move and suppression of motor execution, and that different loci in this cortical area are respectively active for the functions of different sensory modalities.     

Audiogenic kindling increases neuronal responses to acoustic stimuli in neurons of the medial geniculate body of the genetically epilepsy-prone rat

Frequent repetition of audiogenic seizure (AGS) (‘AGS kindling’) in the severe substrain of genetically epilepsy-prone rats (GEPR-9s) results in the appearance of cortical epileptiform electrographic activity, increases of seizure duration and additional convulsive behaviors. These findings suggest that the initial AGS network, which is located primarily in the brainstem, has undergone expansion to the forebrain. The medial geniculate body (MGB) is a thalamic structure that is the first major auditory nucleus efferent to the AGS-initiating site in the inferior colliculus. The MGB is not required for AGS induction, but it has been implicated in the expanded AGS network in GEPR-9s based on focal, pharmacological blockade experiments. The present study examined changes in acoustically evoked MGB neuronal responses in awake and behaving GEPR-9s and in anesthetized GEPR-9s after 14 repetitive AGS-inducing stimuli given daily. An elevated number of action potentials was observed in the MGB neuronal responses after AGS kindling in GEPR-9s. This increase of MGB neuronal responses was associated with a loss of habituation and lasted for at least 28 days after the 14th AGS. An increase in the incidence of sustained acoustic responses in MGB neurons was observed after repetitive AGS in GEPR-9s. Increases in the peak latency and threshold of MGB neuronal responses were also observed after AGS kindling. MGB neurons exhibited a rapid tonic firing during tonic seizures in behaving GEPR-9s, suggesting that the MGB may be implicated in the propagation of seizure activity. However, MGB neuronal firing was silent during post-tonic clonus, a behavior seen in GEPR-9s only after AGS repetition, suggesting that MGB does not play a direct role in the generation of this convulsive behavior. Thus, changes in neuronal firing in nuclei efferent to the MGB, in the expanded neuronal network for repetitive AGS, may be responsible for the generation of post-tonic clonus in GEPR-9s.     

Changes in neuronal activity related to the repetition and relative familiarity of visual stimuli in rhinal and adjacent cortex of the anaesthetised rat

Employing the same techniques as have been used with conscious rats, this study describes neuronal responses signalling information concerning the prior occurrence of visual stimuli in unconscious rats. Recordings of the activity of 387 neurones were made while anaesthetised rats were shown objects. Changes in neuronal responses related to stimulus repetition and the relative familiarity of visual stimuli were sought. The areas sampled were lateral occipital cortex, area TE of temporal cortex, perirhinal cortex and the hippocampal formation. The response to the first presentations of unfamiliar objects was significantly different from that to their second presentations for 30 (35%) of 86 visually responsive neurones; for 23 of the neurones was smaller when the stimulus was repeated, whereas for 7 it was larger. For all of these neurones the response change was maintained across intervening trials on which other stimuli were shown. For 4 (25%) of 16 neurones so tested, the response decrement persisted across at least 10 intervening trials. The activity of 63 neurones was recorded while rats were shown highly familiar as well as unfamiliar objects. The response to unfamiliar objects was significantly different from that to highly familiar objects for 3 (23%) of 13 visually responsive neurones. The types of neuronal response and their incidence expressed as a proportion of the number of visually responsive neurones were similar to those found in unanaesthetised rats (though the proportion of visually responsive neurones encountered in the anaesthetised rat was lower). The results indicate that information concerning the prior occurrence of stimuli is processed even under anaesthesia.     

Differential depressive action of two μ and δ opioid ligands on neuronal responses to noxious stimuli in the thalamic ventrobasal complex of rat

In the present investigation the effects of selective agonists for μ (Tyr- -Ala-Me-Phe-Gly-ol (DAGO)) and δ (Tyr- -Thr-Gly-Phe-Leu-Thr (DTLET)) opioid receptors on neuronal activities induced by noxious cutaneous stimuli in the rat ventrobasal (VB) thalamus were analyzed. The two agonists produced a clear depressive action on thermal as well as mechanical noxious stimuli. The depressive action of DTLET (3 mg/kg i.v.) was lower and of shorter duration than that of DAGO (2 mg/kg i.v.). However, this effect is unambiguously related to the selective stimulation of opioid receptors since a consistent effect was also observed for a dose as low as 1.5 mg/kg i.v. of DTLET. Moreover, DTLET effect needs a high concentration of naloxone (0.5 mg/kg i.v.) to be reversed, while DAGO effect is totally reversed with 0.1 mg/kg i.v.