Abstract:We have studied how rewards modulate the occurrence of microsaccades by manipulating the size of an expected reward and the location of the cue that sets the expectations for future reward. We found an interaction between the size of the reward and the location of the cue. When monkeys fixated on a cue that signaled the size of future reward, the frequency of microsaccades was higher if the monkey expected a large vs. a small reward. When the cue was presented at a site in the visual field that was remote from… Show more
“…As shown in these examples, microsaccades were observed in a few trials around 200-300 ms after stimulus onset, consistent with previous studies (Hafed et al, 2011;Tian et al, 2016). A recent study reported that microsaccades usually occur after the presentation of cues associated with large, but not small, reward in monkeys (Joshua et al, 2015). This suggests that microsaccades occur less frequently in response to visual stimuli associated with no reward, consistent with the present study in which only responses to the sample stimuli associated with no reward were analyzed in the DNMS task.…”
Section: Analysis Of Sc Neuronal Responsessupporting
Human babies respond preferentially to faces or face-like images. It has been proposed that an innate and rapid face detection system is present at birth before the cortical visual pathway is developed in many species, including primates. However, in primates, the visual area responsible for this process is yet to be unraveled. We hypothesized that the superior colliculus (SC) that receives direct and indirect retinal visual inputs may serve as an innate rapid face-detection system in primates. To test this hypothesis, we examined the responsiveness of monkey SC neurons to first-order information of faces required for face detection (basic spatial layout of facial features including eyes, nose, and mouth), by analyzing neuronal responses to line drawing images of: (1) face-like patterns with contours and properly placed facial features; (2) non-face patterns including face contours only; and (3) nonface random patterns with contours and randomly placed face features. Here, we show that SC neurons respond stronger and faster to upright and inverted face-like patterns compared to the responses to nonface patterns, regardless of contrast polarity and contour shapes. Furthermore, SC neurons with central receptive fields (RFs) were more selective to face-like patterns. In addition, the population activity of SC neurons with central RFs can discriminate face-like patterns from nonface patterns as early as 50 ms after the stimulus onset. Our results provide strong neurophysiological evidence for the involvement of the primate SC in face detection and suggest the existence of a broadly tuned template for face detection in the subcortical visual pathway.
“…As shown in these examples, microsaccades were observed in a few trials around 200-300 ms after stimulus onset, consistent with previous studies (Hafed et al, 2011;Tian et al, 2016). A recent study reported that microsaccades usually occur after the presentation of cues associated with large, but not small, reward in monkeys (Joshua et al, 2015). This suggests that microsaccades occur less frequently in response to visual stimuli associated with no reward, consistent with the present study in which only responses to the sample stimuli associated with no reward were analyzed in the DNMS task.…”
Section: Analysis Of Sc Neuronal Responsessupporting
Human babies respond preferentially to faces or face-like images. It has been proposed that an innate and rapid face detection system is present at birth before the cortical visual pathway is developed in many species, including primates. However, in primates, the visual area responsible for this process is yet to be unraveled. We hypothesized that the superior colliculus (SC) that receives direct and indirect retinal visual inputs may serve as an innate rapid face-detection system in primates. To test this hypothesis, we examined the responsiveness of monkey SC neurons to first-order information of faces required for face detection (basic spatial layout of facial features including eyes, nose, and mouth), by analyzing neuronal responses to line drawing images of: (1) face-like patterns with contours and properly placed facial features; (2) non-face patterns including face contours only; and (3) nonface random patterns with contours and randomly placed face features. Here, we show that SC neurons respond stronger and faster to upright and inverted face-like patterns compared to the responses to nonface patterns, regardless of contrast polarity and contour shapes. Furthermore, SC neurons with central receptive fields (RFs) were more selective to face-like patterns. In addition, the population activity of SC neurons with central RFs can discriminate face-like patterns from nonface patterns as early as 50 ms after the stimulus onset. Our results provide strong neurophysiological evidence for the involvement of the primate SC in face detection and suggest the existence of a broadly tuned template for face detection in the subcortical visual pathway.
“…Saccades but not spiking increased following reward delivery. After cue presentation, fixational saccades were modulated by reward (Joshua et al, 2015), but this modulation did not affect the Cspk response to the cue (Figure 3—figure supplement 2C,D). The cells that discriminated between the large and small rewards after cue presentation responded similarly in trials with and without saccades.…”
Section: Resultsmentioning
confidence: 99%
“…10.7554/eLife.46870.009Figure 3—figure supplement 2.Saccades and microsaccades do not underpin the Cspk rate difference during the cue.( A and B ) The saccade rate as a function of time from the cue onset ( A ) and reward delivery ( B ) for trials with large (blue) and small (red) rewards. After cue onset, the monkeys made more fixational saccades in the large reward condition (Joshua et al, 2015). The large increase after reward delivery is a result of the monkeys' saccade back to the center of the screen from the eccentric position of the eye.…”
Climbing fiber inputs to the cerebellum encode error signals that instruct learning. Recently, evidence has accumulated to suggest that the cerebellum is also involved in the processing of reward. To study how rewarding events are encoded, we recorded the activity of climbing fibers when monkeys were engaged in an eye movement task. At the beginning of each trial, the monkeys were cued to the size of the reward that would be delivered upon successful completion of the trial. Climbing fiber activity increased when the monkeys were presented with a cue indicating a large reward, but not a small reward. Reward size did not modulate activity at reward delivery or during eye movements. Comparison between climbing fiber and simple spike activity indicated different interactions for coding of movement and reward. These results indicate that climbing fibers encode the expected reward size and suggest a general role of the cerebellum in associative learning beyond error correction.
“…We previously reported that neurons in the monkey PPTg showed saccade-related activity modulation, some modulations were only associated with reward-related saccades consistent with neurons reported in the basal ganglia (Kobayashi et al, 2002; Okada and Kobayashi, 2009), while others exhibited this modulation with every saccade, including small fixational saccades, consistent with neurons in the cerebellum (Okada and Kobayashi, 2014). One possibility is that the PPTg acts as an interface between the basal ganglia and cerebellum, and thus reward and cognitive signals influence precise microsaccades (Joshua et al, 2015; Yu et al, 2016). Analyzing saccade-associated neuronal activity may be a key tool for understanding the roles of PPTg within the cerebellar and basal ganglia networks in health and disease conditions.…”
Section: Therapeutic Effect Of Pptg Stimulation In Parkinson’s Diseasementioning
As an important component of ascending activating systems, brainstem cholinergic neurons in the pedunculopontine tegmental nucleus (PPTg) are involved in the regulation of motor control (locomotion, posture and gaze) and cognitive processes (attention, learning and memory). The PPTg is highly interconnected with several regions of the basal ganglia, and one of its key functions is to regulate and relay activity from the basal ganglia. Together, they have been implicated in the motor control system (such as voluntary movement initiation or inhibition), and modulate aspects of executive function (such as motivation). In addition to its intimate connection with the basal ganglia, projections from the PPTg to the cerebellum have been recently reported to synaptically activate the deep cerebellar nuclei. Classically, the cerebellum and basal ganglia were regarded as forming separated anatomical loops that play a distinct functional role in motor and cognitive behavioral control. Here, we suggest that the PPTg may also act as an interface device between the basal ganglia and cerebellum. As such, part of the therapeutic effect of PPTg deep brain stimulation (DBS) to relieve gait freezing and postural instability in advanced Parkinson’s disease (PD) patients might also involve modulation of the cerebellum. We review the anatomical position and role of the PPTg in the pathway of basal ganglia and cerebellum in relation to motor control, cognitive function and PD.
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