During natural viewing, we often recognize multiple objects, detect their motion, and select one object as the target to track. It remains to be determined how such behavior is guided by the integration of visual form and motion perception. To address this, we studied how monkeys made a choice to track moving targets with different forms by smooth pursuit eye movements in a two-target task. We found that pursuit responses were biased toward the motion direction of a target with a hole. By computing the relative weighting, we found that the target with a hole exhibited a larger weight for vector computation. The global hole feature dominated other form properties. This dominance failed to account for changes in pursuit responses to a target with different forms moving singly. These findings suggest that the integration of visual form and motion perception can reshape the competition in sensorimotor networks to guide behavioral selection.
Animals ; Pursuit, Smooth ; Macaca mulatta ; Motion Perception/physiology* ; Photic Stimulation

Studies have shown that spatial attention remarkably affects the trial-to-trial response variability shared between neurons. Difficulty in the attentional task adjusts how much concentration we maintain on what is currently important and what is filtered as irrelevant sensory information. However, how task difficulty mediates the interactions between neurons with separated receptive fields (RFs) that are attended to or attended away is still not clear. We examined spike count correlations between single-unit activities recorded simultaneously in the primary visual cortex (V1) while monkeys performed a spatial attention task with two levels of difficulty. Moreover, the RFs of the two neurons recorded were non-overlapping to allow us to study fluctuations in the correlated responses between competing visual inputs when the focus of attention was allocated to the RF of one neuron. While increasing difficulty in the spatial attention task, spike count correlations were either decreased to become negative between neuronal pairs, implying competition among them, with one neuron (or none) exhibiting attentional enhancement of firing rate, or increased to become positive, suggesting inter-neuronal cooperation, with one of the pair showing attentional suppression of spiking responses. Besides, the modulation of spike count correlations by task difficulty was independent of the attended locations. These findings provide evidence that task difficulty affects the functional interactions between different neuronal pools in V1 when selective attention resolves the spatial competition.
Animals ; Attention/physiology* ; Macaca mulatta ; Neurons/physiology* ; Photic Stimulation ; Primary Visual Cortex ; Visual Cortex/physiology*

Active exploratory behaviors have often been associated with theta oscillations in rodents, while theta oscillations during active exploration in non-human primates are still not well understood. We recorded neural activities in the frontal eye field (FEF) and V4 simultaneously when monkeys performed a free-gaze visual search task. Saccades were strongly phase-locked to theta oscillations of V4 and FEF local field potentials, and the phase-locking was dependent on saccade direction. The spiking probability of V4 and FEF units was significantly modulated by the theta phase in addition to the time-locked modulation associated with the evoked response. V4 and FEF units showed significantly stronger responses following saccades initiated at their preferred phases. Granger causality and ridge regression analysis showed modulatory effects of theta oscillations on saccade timing. Together, our study suggests phase-locking of saccades to the theta modulation of neural activity in visual and oculomotor cortical areas, in addition to the theta phase locking caused by saccade-triggered responses.
Animals ; Frontal Lobe/physiology* ; Macaca mulatta ; Neurons/physiology* ; Saccades ; Theta Rhythm ; Visual Fields

Recent work in decision neuroscience suggests that visual saliency can interact with reward-based choice, and the lateral intraparietal cortex (LIP) is implicated in this process. In this study, we recorded from LIP neurons while monkeys performed a two alternative choice task in which the reward and luminance associated with each offer were varied independently. We discovered that the animal's choice was dictated by the reward amount while the luminance had a marginal effect. In the LIP, neuronal activity corresponded well with the animal's choice pattern, in that a majority of reward-modulated neurons encoded the reward amount in the neuron's preferred hemifield with a positive slope. In contrast, compared to their responses to low luminance, an approximately equal proportion of luminance-sensitive neurons responded to high luminance with increased or decreased activity, leading to a much weaker population-level response. Meanwhile, in the non-preferred hemifield, the strength of encoding for reward amount and luminance was positively correlated, suggesting the integration of these two factors in the LIP. Moreover, neurons encoding reward and luminance were homogeneously distributed along the anterior-posterior axis of the LIP. Overall, our study provides further evidence supporting the neural instantiation of a priority map in the LIP in reward-based decisions.
Animals ; Macaca mulatta/physiology* ; Parietal Lobe ; Neurons/physiology* ; Saccades ; Reward ; Photic Stimulation

OBJECTIVETo observe the specificity relationship between acupuncture at "Hegu" (LI 4) and the facial muscular movement in rhesus monkeys under the physiological state by using neuromuscular electrical measurement technique.

METHODSEighteen rhesus monkeys were randomized into a Hegu group, a Houxi group and a Waiguan group, 6 monkeys in each one. Under the physiological state, EMG was detected on the frontal muscle, zygomatic muscle and orbicular muscle before and after acupuncture at different acupoints. The impacts of acupuncture on the facial EMG were studied and compared among different acupoints.

RESULTSWith acupuncture at "Hegu" (LI 4), the latency was reduced (P < 0.01) and the peak value and area were increased (P < 0.05, P < 0.01) in the frontal EMG; the area and the peak value were increased (P < 0.01, P < 0.05) and latency was reduced (P < 0.05) in the zygomatic EMG; the frequency was increased (P < 0.01) and the latency was reduced (P < 0.05) in the orbicular EMG. Before and after acupuncture at "Hegu" (LI 4), the change rates of EMG frequency, peak value, area and latency on the frontal, zygomatic and orbicular muscles were higher than those at "Houxi" (SI 3) and "Waiguan" (TE 5) (P < 0.05, P < 0.01) separately.

CONCLUSIONThe relative specificity presents between Hegu (LI 4) and facial muscular movement.

Acupuncture Points ; Acupuncture Therapy ; Animals ; Electromyography ; Face ; physiology ; Female ; Humans ; Macaca mulatta ; Male ; Models, Animal

OBJECTIVETo evaluate the influence of mandibular distraction osteogenesis on inferior alveolar nerve function.

METHODS16 young Macaca rhesus monkeys were used as experiment animals. 5 days after mandibular osteotomy under general anesthesia, 10 male monkeys were distracted at right side and 6 females were bilaterally distracted at a rate of 0.5 mm x 2/day, for 15 days. The mandible was lengthened to an average of 13.5 mm. The Sensory Nerve Action Potential (SNAP) test was successfully applied in 16 monkeys before operation and at 0, 2, 4, 6, 9 and 12 weeks after distraction finished. Eight-channel EMG equipment was used for SNAP wave recording. The recordings were made with needle electrodes at foramen ovale and the stimulation was done at the mental foramen with two surface electrodes. The metal ground electrode was fixed on the right forearm. The stimulation intensities were five times of thresholds of each animal. The latency was measured at the first wave peak and the amplitude was measured between two wave peaks.

RESULTSJust after distraction finished, the latency period was 22.18% longer than before operation and gradually shortened as time lapsed. When distraction finished, the amplitude of SNAP wave was only 28.54% of that before operation, and after 12 weeks, it increased to the level of 99.84% of that before operation.

CONCLUSIONSThe mandibular distraction osteogenesis has temporary influence on the function of inferior alveolar nerve, but it is little and reversible, along with the regeneration of nerve sheath and axon, the nerve function can gradually return to normal level.

Action Potentials ; Animals ; Female ; Macaca mulatta ; Male ; Mandible ; surgery ; Mandibular Nerve ; physiology ; Nerve Regeneration ; Osteogenesis, Distraction

Animals ; Macaca mulatta ; Nerve Regeneration ; Peripheral Nerve Injuries ; physiopathology ; Peripheral Nerves ; physiology ; Rats

Prepulse inhibition (PPI) refers to a decreased response to a startling stimulus when another weaker stimulus precedes it. Most PPI studies have focused on the physiological startle reflex and fewer have reported the PPI of cortical responses. We recorded local field potentials (LFPs) in four monkeys and investigated whether the PPI of auditory cortical responses (alpha, beta, and gamma oscillations and evoked potentials) can be demonstrated in the caudolateral belt of the superior temporal gyrus (STGcb). We also investigated whether the presence of a conspecific, which draws attention away from the auditory stimuli, affects the PPI of auditory cortical responses. The PPI paradigm consisted of Pulse-only and Prepulse + Pulse trials that were presented randomly while the monkey was alone (ALONE) and while another monkey was present in the same room (ACCOMP). The LFPs to the Pulse were significantly suppressed by the Prepulse thus, demonstrating PPI of cortical responses in the STGcb. The PPI-related inhibition of the N1 amplitude of the evoked responses and cortical oscillations to the Pulse were not affected by the presence of a conspecific. In contrast, gamma oscillations and the amplitude of the N1 response to Pulse-only were suppressed in the ACCOMP condition compared to the ALONE condition. These findings demonstrate PPI in the monkey STGcb and suggest that the PPI of auditory cortical responses in the monkey STGcb is a pre-attentive inhibitory process that is independent of attentional modulation.
Animals ; Auditory Cortex ; physiology ; Evoked Potentials, Auditory ; physiology ; Macaca mulatta ; Male ; Prepulse Inhibition ; physiology ; Temporal Lobe ; physiology

BACKGROUNDFew studies have focused on peripheral nerve conduction during exposure to microgravity. The -6° head-down tilt (HDT) comprises an experimental model used to simulate the space flight environment. This study investigated nerve conduction characteristics of rhesus monkeys before and after prolonged exposure to HDT.

METHODSSix rhesus monkeys (3-4 years old) were tilted backward 6° from the horizontal. Nerve conduction studies (NCSs) were performed on the median, ulnar, tibial, and fibular motor nerves. Analysis of variance with a randomized block design was conducted to compare the differences in the NCS before and 7, 21, and 42 days after the -6° HDT.

RESULTSThe proximal amplitude of the CMAP of the median nerve was significantly decreased at 21 and 42 days of HDT compared with the amplitude before HDT (4.38 ± 2.83 vs. 8.40 ± 2.66 mV, F = 4.85, P = 0.013 and 3.30 ± 2.70 vs. 8.40 ± 2.66 mV, F = 5.93, P = 0.004, respectively). The distal amplitude of the CMAP of the median nerve was significantly decreased at 7, 21, and 42 days of HDT compared with the amplitude before HDT (7.28 ± 1.27 vs. 10.25 ± 3.40 mV, F = 4.03, P = 0.039; 5.05 ± 2.01 vs. 10.25 ± 3.40 mV, F = 6.25, P = 0.04; and 3.95 ± 2.79 vs. 10.25 ± 3.40 mV, F = 7.35, P = 0.01; respectively). The proximal amplitude of the CMAP of the tibial nerve was significantly decreased at 42 days of HDT compared with the amplitude before HDT (6.14 ± 1.94 vs. 11.87 ± 3.19 mV, F = 5.02, P = 0.039).

CONCLUSIONSThis study demonstrates that the compound muscle action potential amplitudes of nerves are decreased under simulated microgravity in rhesus monkeys. Moreover, rhesus monkeys exposed to HDT might be served as an experimental model for the study of NCS under microgravity.

Action Potentials ; physiology ; Animals ; Female ; Head-Down Tilt ; physiology ; Macaca mulatta ; Male ; Neural Conduction ; physiology ; Weightlessness Simulation

Animal's numerical competence has been one of the central issues in comparative psychology, cognitive psychology and cognitive neuroscience. A great number of studies indicate that animals have the capability to subitize small numerousness and judge relative numerousness. However, it is pendent if they have the counting ability. There is no evidence that animals can estimate numerousness. Neurophysiological studies show that the posterior parietal cortex and the prefrontal cortex in monkeys are involved in the neural mechanisms underlying numerical competence.
Animals ; Behavior, Animal ; Cerebral Cortex ; physiology ; Cognition ; Macaca mulatta ; Mathematics ; Mental Competency ; Pattern Recognition, Visual ; physiology ; Verbal Behavior ; physiology