Tactile and visual sense system interactions: a developmental study using reaction time models.
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Sensory system interactions during simultaneous vestibular and visual stimulation in PET.
The patterns of regional cerebral blood flow (rCBF) increases and decreases in PET were compared for unimodal vestibular, unimodal visual, and for simultaneous vestibular and visual stimulation. Thirteen healthy volunteers were exposed to a) caloric vestibular stimulation, b) small-field visual motion stimulation in roll, c) simultaneous caloric vestibular and visual pattern stimulation. Unimodal vestibular stimulation led to activations of vestibular cortex areas, in particular the parieto-insular vestibular cortex (PIVC), and concurrent deactivations of visual cortical areas [Brodmann area (BA) 17-19]. Unimodal visual motion stimulation led to activations of the striate visual cortex and the motion-sensitive area in the middle temporal/middle occipital gyri (BA 19/37) with concurrent deactivations in the PIVC. Simultaneous bimodal stimulation resulted in activations of the cortical representation of both sensory modalities. In the latter condition activations and deactivations were significantly smaller compared to unimodal stimulation. The findings are consistent with the concept of an inhibitory reciprocal vestibulo-visual interaction in all three stimulus conditions.
Adult↗
Monkey hippocampal neuron responses to complex sensory stimulation during object discrimination.
The purpose of this study was to investigate, during the performance of an object discrimination task, responses of neurons in the monkey hippocampal formation to the sight of several objects that have biological meaning, and compare these responses with those of amygdalar neurons studied previously using the same task. Neuronal activity in the hippocampal formation of conscious monkeys was recorded during performance of a task that led to presentation of familiar rewarding, familiar aversive, or unfamiliar objects. Of 864 neurons recorded in the hippocampal formation and adjacent cortices, 160 (18.5%) responded to the sight of a certain object(s). Responses to the sight of different kinds of objects were analyzed in detail. Nondifferential neurons (n = 73) responded to different objects with no significant difference in response magnitudes, and differential neurons (n = 87) responded to different objects with different response magnitudes. Of the differential neurons, 23 responded more strongly to rewarding objects than to other objects (rewarding-object-dominant neurons), but the magnitude of responses to objects did not necessarily correlates with the order of preferences to the objects as determined from observation of animal behavior. Aversive-object-dominant neurons (n = 13) responded more to aversive objects than to other objects. Unfamiliar-object-dominant neurons (n = 7) responded more to unfamiliar objects than to familiar objects. Selective neurons (n = 10) responded selectively to only one object or one category of objects. Fourteen of the rewarding- or averse-object-dominant neurons were tested in extinction or reversal trials. In 12 of 14 neurons, responses to a rewarding or aversive object did not change, or slightly weakened, in extinction or reversal trials. The results suggest the following. (1) Responses of rewarding- or aversive-object-dominant neurons may be involved in object-reward or object-aversion association. However, responses of many of these neurons might reflect past inputs to reinforcement rather than extant emotional processing. (2) Responses of unfamiliar-object-dominant neurons may be involved in recognition of objects based on their familiar or unfamiliar aspects. These results are further discussed and compared with responsiveness of amygdalar neurons.
Acoustic Stimulation↗
Artifacts due to stimulus correlated motion in functional imaging of the brain.
To assess the effect of stimulus correlated motion on the appearance of functional magnetic resonance images, conventional visual and motor protocols were each performed by four normal volunteers and an image co-registration technique was used to retrospectively monitor subject motion. In three studies synthetic data sets were constructed from single baseline images using the positional information obtained from the co-registration procedure. Cumulative difference images were then created from both the synthetic and functional image sets. Stimulus correlated motion was detected in all eight studies and the synthetic cumulative difference images showed striking similarities to the equivalent functional images in each case.
Adult↗
Female orgasm rate increases with male dominance in Japanese macaques.
Under specific circumstances, nonhuman primate females may experience orgasm. The occurrence of female copulatory orgasm appears to be highly variable, however, and its proximate causation is poorly understood. We investigated the proximate mechanisms that control orgasmic response in female macaques. During 238 h of observation of sexual behaviour in a large captive group of Japanese macaques, Macaca fuscata, 240 copulations were recorded involving 68 different heterosexual pairs formed by 16 males and 26 females. Female orgasmic responses were observed in 80 of 240 copulations (33%). The frequency of orgasms was not correlated with female age or dominance rank, but it was higher for copulations lasting longer and involving a higher number of mounts and pelvic thrusts. When the level of physical stimulation experienced by females during copulation was statistically controlled, the highest frequency of female orgasms was found among pairs formed by high-ranking males and low-ranking females and the lowest frequency among pairs formed by low-ranking males and high-ranking females. These findings suggest that the proximate mechanisms that control orgasmic threshold in female macaques are more responsive to social stimuli and less constrained by physiological limitations than previously thought. Copyright 1998 The Association for the Study of Animal Behaviour.
Journal Article↗
Somatic correlates of adrenergic activity during aggression in the lizard, Anolis carolinensis.
Aggressive interactions in Anolis carolinensis result in increased circulating levels of epinephrine (Epi) and norepinephrine (NE) and conspicuous color changes. This activation of the adrenergic component of an acute stress response is externally represented by the darkening of the postorbital eyespot of A. carolinensis. In adult males, this site darkens in response to stressful physical stimulation (trauma, passive restraint) or psychological stimuli, most notably the sight of an aggressively intruding conspecific. Aggressive male A. carolinensis exhibit postorbital eyespot darkening; animals that have a longer latency to expression of this eyespot and those that never show this response were defeated in agonistic interactions. Also, during agonistic interactions, subjects that subsequently win are the first to display eyespot darkening. Plasma catecholamine levels are significantly elevated within 30 sec in both combatants. At 30 sec following the determination of the outcome, winning male lizards have plasma NE levels which are higher than those of losers. Castration, however, significantly increases the latency to eyespot darkening and extends its duration. Testosterone levels may therefore enhance the onset of Epi-mediated eyespot darkening as well as other aspects of the endocrine stress response. Elevated androgen levels and more rapid activation of acute catecholamine response increases the likelihood of becoming socially dominant.
Adrenergic Fibers↗
Cortical sites of sustained and divided attention in normal elderly humans.
Human brain mechanisms subserving attention have been assigned to prefrontal, midfrontal, and posterior parietal cortices, as well as to the anterior cingulate and the thalamus. To map these mechanisms in the brain, most studies have used selective attention tasks; few studies have mapped the brain under sustained or divided attention. The present study was designed to create maps of regional activity associated with sustained and divided attention using two different sensory modalities: visual checkerboard stimulation and vibrotactile stimulation of the right hand. Five cerebral PE-tomograms of 15O-labeled water uptake were acquired from 16 elderly healthy subjects during sustained or divided attention to the frequency of stimulation. To locate active brain regions, the t-statistic map of relative changes in cerebral blood flow was coregistered to the subjects' averaged brain MR images and to the standard Talairach brain coordinate system. Attention was associated with activity in two sites, the right middle frontal gyrus (Brodmann area 46) and the right inferior parietal lobule (Brodmann area 40). The frontal site was more active when the subjects attended to the visual stimulus and when the attention was divided, while the parietal site was more active during attention to the vibrotactile stimulus and during simple sustained attention. Our observations are consistent with the hypotheses (1) that the right posterior parietal attention center subserves attention to several sensory modalities and (2) that a cortical network of specific neuronal sites subserves both sustained and divided attention. These hypotheses must be tested in further studies.
Aged↗
A CBF-based event-related brain activation paradigm: characterization of impulse-response function and comparison to BOLD.
A perfusion-based event-related functional MRI method for the study of brain activation is presented. In this method, cerebral blood flow (CBF) was measured using a recently developed multislice arterial spin-labeling (ASL) perfusion imaging method with rapid spiral scanning. Temporal resolution of the perfusion measurement was substantially improved by employing intertrial subtraction and stimulus-shifting schemes. Perfusion and blood oxygenation level-dependent (BOLD) signals were obtained simultaneously by subtracting or adding the control and labeled images, respectively, in the same data sets. The impulse response function (IRF) of perfusion during brain activation was characterized for multiple stimulus durations and compared to the simultaneously acquired BOLD response. The CBF response curve preceded the BOLD curve by 0.21 s in the rising phase and 0.64 s in the falling phase. Linear additivity of the CBF and BOLD responses was assessed with rapidly repeated stimulations within single trials, and departure from linearity was found in both responses, characterized as attenuated amplitude and delayed rising time. Event-related visual and sensorimotor activation experiments were successfully performed with the new perfusion technique.
Brain↗
Transperceptual encoding and retrieval processes in memory: a PET study of visual and haptic objects.
An important objective of functional neuroimaging research is to identify neuroanatomical correlates of memory processes such as encoding and retrieval. In typical studies directed at this goal, however, the to-be-remembered information has been presented in a single perceptual modality. Under these conditions it is not known whether the observed brain activity reflects the studied memory process as such or only the memory process in the given modality. The positron emission tomography (PET) study reported here was designed to identify brain regions involved in encoding and retrieval processes specific to visual and haptic modalities, as well as those common to the two modalities. These latter, common regions, were assumed to be associated with "transperceptual" encoding and retrieval processes. Abstract three-dimensional objects, difficult to describe verbally, served as to-be-remembered materials. A multivariate partial least squares analysis of the PET data revealed that transperceptual encoding processes activated right medial temporal lobe, superior prefrontal cortex bilaterally, and posterior inferior temporal gyrus bilaterally. Transperceptual recognition activations were observed in two right orbitofrontal regions and in anterior cingulate. These results provide initial evidence that some processes involved in memory encoding and retrieval operate beyond perceptual processes and in that sense are transperceptual.
Adult↗
Physiology and morphology of descending neurons in pheromone-processing olfactory pathways in the male moth Manduca sexta.
1. We have characterized the responses and structure of olfactory descending neurons (DNs) that reside in the protocerebrum (PC) of the brain of male sphinx moths Manduca sexta and project toward thoracic ganglia. 2. Excitatory responses of DNs to pheromone blends were of two general types: (a) brief excitation (BE) that recovered to background in less than 1 s after the stimulus, and (b) long-lasting excitation (LLE) that outlasted the stimulus by greater than or equal to 1 s and, in many cases, as long as 30 s. Individual pheromone components were ineffective in eliciting LLE. 3. Some neurons showing LLE also exhibited state-dependent responses to pheromonal stimuli. When such neurons were in a state of low background firing, stimulation with pheromone blend elicited LLE. When they were in a state of LLE, an identical stimulus reduced firing for 5-10 s after which firing gradually increased to the initial higher level. 4. Thirteen stained DNs were reconstructed from serial sections for detailed analysis of their morphology in the brain. DNs exhibiting LLE had neurites concentrated in the lateral accessory lobes (LALs) in the protocerebrum and adjacent neuropil. Most DNs exhibiting only BE to pheromonal stimuli and other DNs showing responses only to visual or mechanosensory stimuli did not have branches in the LALs.
Animals↗
A model of synchronization of motor acts to a stimulus sequence. I. Timing and error corrections.
A closed-loop timing model is proposed that accounts for several phenomena observed in tasks which require production of a sequence of motor acts in synchrony with a sequence of stimuli. In contrast to the previous models, variables available to the central nervous system of a subject (internal variables) and externally measurable variables are distinguished, and several physiologically justifiable internal variables are included. The model assumes the existence of (a) an internal timekeeper producing a reference interval that is used in a motor-control unit for timing of the next motor command; (b) an intrinsic (subjective) synchrony that relies on some a posteriori (feedback) information about the already executed onset of the motor act. A two-way error-corrective mechanism is hypothesized: (1) period (inverted frequency) corrections--the reference interval (period) is set at the beginning of the task according to the interstimulus-onset interval(s) and later corrected for differences between its duration and the actual duration of s; (2) phase corrections--internal synchronization errors (i.e., time gaps between the central temporal availability of internal representations of stimuli and of some feedback aspect of responses) are corrected for directly in the motor-control unit. Objectively measured systematic asynchrony of responses and stimuli is determined by the internal delays in information transduction. Finally, the model is used for making predictions of a subject's performance in some other experimental settings of the synchronization task.
Acoustic Stimulation↗
Sensory evoked potentials in unanesthetized unrestrained cuttlefish: a new preparation for brain physiology in cephalopods.
Up to five microelectrodes inserted through short hypodermic needles in the cranial cartilage of Sepia officinalis recorded potentials while the cuttlefish moved freely in a small enclosure. Compound field potentials and unit spikes were seen during ongoing, spontaneous activity and after sensory stimulation. Ongoing activity resembles that reported for octopus, with maximum power usually below 20 Hz. Amplitude varies greatly but has not been seen to shut off or turn on abruptly and globally as in octopus. Evoked potentials, focally large after flashes of light consist of several waves; the first is largest, positive and peaks at ca. 35 ms (called P35), followed by ca. P75, P95, N110 and smaller waves or oscillations lasting more than 0.5 s. The Upper Following Frequency (highest flashing rate the potentials can follow 1:1), without averaging, is greater than 15 flashes/s (20-22 degrees C); at 20/s the 1:1 following lasts for 1 or 2 s. The Lower Fusion Frequency of averaged responses is less than 30/s. Gentle tapping of the tank wall evokes local, brief, fast potentials. No responses have been found to loud air-borne clicks and tone bursts with principal energy at 300 Hz or to electric fields in the bath at 50-100 microV/cm. In a few loci relatively large slow Omitted Stimulus Potentials have been seen following the end of a train of flashes at more than 5/s; these are by definition event related potentials and a special, central form of OFF response.
Animals↗
Sensory interactions in the anterior ectosylvian cortex of cats.
Sensory interactions, namely, the responses of single cells to stimulations originating from the two sides of the body or from the two visual fields, or from more than one sensory modality (namely, visual, auditory and somatosensory), were evaluated within the anterior ectosylvian cortex (AEC) of cats. Results showed that responses of single neurons to a stimulus of one modality can be enhanced or inhibited by the presentation of another stimulus of either the same or another modality. This facilitatory or inhibitory modulation seems to depend upon temporal and/or spatial relationships between the stimuli. These results, taken together with those previously obtained in our laboratory and by others, suggest that neurons in the AEC may be involved in integrating inputs from various modalities and possibly linking sensory input with action.
Acoustic Stimulation↗
Factors influencing neural activity in parabrachial regions during cat vocalizations.
The parabrachial nucleus in mammals is intimately connected with other vocalization controlling brainstem structures. It, along with ventromedially adjacent structures, also has been identified as the pneumotaxic center, and as such shows strong respiratory related activity in the anesthetized cat. The current study examines the neuronal activity in cat parabrachial regions during production of instrumentally conditioned vocalizations. Most of the units in our sample show considerable activity during periods between vocalizations. For many units, firing rate fluctuates during the respiratory cycle, although apparently not as strongly as reported in the decerebrate cat. Also, there is often strong phasic activity during periods where animals are licking to ingest their food rewards. During the peri-vocalization period, various neural activity patterns can be recorded. Most common is an activity increase during the vocalization itself. Moreover, in some units, this activity increase has an auditory component. A smaller number of units show other activity patterns, including a suppression of activity during vocalization and activity increases preceding the vocalization. Overall, our results suggest that the parabrachial region's involvement in vocal control is quite complex, involving convergence of respiratory, acoustic, vocalization-related, and perhaps somatosensory influences.
Acoustic Stimulation↗
A bimodal map of space: somatosensory receptive fields in the macaque putamen with corresponding visual receptive fields.
The macaque putamen contains neurons that respond to somatosensory stimuli such as light touch, joint movement, or deep muscle pressure. Their receptive fields are arranged to form a map of the body. In the face and arm region of this somatotopic map we found neurons that responded to visual stimuli. Some neurons were bimodal, responding to both visual and somatosensory stimuli, while others were purely visual, or purely somatosensory. The bimodal neurons usually responded to light cutaneous stimulation, rather than to joint movement or deep muscle pressure. They responded to visual stimuli near their tactile receptive field and were not selective for the shape or the color of the stimuli. For cells with tactile receptive fields on the face, the visual receptive field subtended a solid angle extending from the tactile receptive field to about 10 cm. For cells with tactile receptive fields on the arm, the visual receptive field often extended further from the animal. These bimodal properties provide a map of the visual space that immediately surrounds the monkey. The map is organized somatotopically, that is, by body part, rather than retinotopically as in most visual areas. It could function to guide movements in the animal's immediate vicinity. Cortical areas 6, 7b, and VIP contain bimodal cells with very similar properties to those in the putamen. We suggest that the bimodal cells in area 6, 7b, VIP, and the putamen form part of an interconnected system that represents extra personal space in a somatotopic fashion.
Acoustic Stimulation↗
Pattern of extraocular muscle activation during reflex blinking.
Studies in humans and rabbits suggest that cocontraction of extraocular muscles occurs with reflex and voluntary blinks. We determined the pattern of extraocular muscle activity elicited by blink-evoking visual and trigeminal stimuli by electromyographically recording antagonistic pairs of extraocular muscles in alert rabbits. In addition, we recorded the activity of antidromically identified oculomotor motoneurons in response to the same stimuli in alert rabbits. The data demonstrate that all extraocular muscles except the superior oblique transiently increase their activity in response to blink-evoking stimuli. The pattern of extraocular muscle activity with reflex blinks mirrors that occurring in the lid-closing muscle, orbicularis oculi, but the latency of extraocular muscle activation is longer.
Animals↗
Neurons signalling the maintenance of attentive fixation in frontal area 6a beta of macaque monkey.
Twelve out of 140 neurons recorded in a restricted region of the frontal agranular cortex (area 6a beta) of trained macaque monkeys, discharged only during attentive fixation of a target in the straight ahead position. These cells, lacking a visual receptive field, were silent when the animal's eye was in the same position during spontaneous oculomotor behaviour. Our preliminary results suggest that this area is involved in the codification of attentive fixation.
Acoustic Stimulation↗
Haptic localization and the internal representation of the hand in space.
As the hand actively explores the environment, contact with an object leads to neuronal activity in the topographic maps of somatosensory cortex. However, the brain must combine this somatotopically encoded tactile information with an internal representation of the hand's location in space if it is to determine the position of the object in three-dimensional space (3-D haptic localization). To investigate the fidelity of this internal representation in human subjects, a small tactual stimulator, light enough to be worn on the subject's hand, was used to present a brief mechanical pulse (6-ms duration) to the right index finger before, during, or after a fast, visually evoked movement of the right hand. In experiment 1, subjects responded by pointing to the perceived location of the mechanical stimulus in 3-D space. Stimuli presented shortly before or during the visually evoked movement were systematically mislocalized, with the reported location of the stimulus approximately equal to the location occupied by the hand 90 ms after stimulus onset. This pattern of errors indicates a representation of the movement that fails to account for the change in the hand's location during somatosensory delays and, in some subjects, inaccurately depicts the velocity of the actual movement. In experiment 2, subjects were instructed to verbally indicate the perceived temporal relationship of the stimulus and the visually evoked movement (i.e., by reporting whether the stimulus was presented "before," "during," or "after" the movement). On average, stimuli presented in the 38-ms period before movement onset were more likely to be perceived as having occurred during rather than before the movement. Similarly, stimuli in the 145-ms period before movement termination were more likely to be perceived as having occurred after rather than during the movement. The analogous findings of experiments 1 and 2 indicate that the same inaccurate representation of dynamic hand position is used to both localize tactual stimuli in 3-D space and construct the perception of arm movement.
Adult↗