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At least 685 records · Page 38Linked to original sources
PubMed1997

Human heading estimation during visually simulated curvilinear motion.

Recent studies have suggested that humans cannot estimate their direction of forward translation (heading) from the resulting retinal motion (flow field) alone when rotation rates are higher than approximately 1 deg/sec. It has been argued that either oculomotor or static depth cues are necessary to disambiguate the rotational and translational components of the flow field and, thus, to support accurate heading estimation. We have re-examined this issue using visually simulated motion along a curved path towards a layout of random points as the stimulus. Our data show that, in this curvilinear motion paradigm, five of six observers could estimate their heading relatively accurately and precisely (error and uncertainty < approximately 4 deg), even for rotation rates as high as 16 deg/sec, without the benefit of either oculomotor or static depth cues signaling rotation rate. Such performance is inconsistent with models of human self-motion estimation that require rotation information from sources other than the flow field to cancel the rotational flow.

Adult↗
PubMed1998

Second-order motions contribute to vection.

First- and second-order motions differ in their ability to induce motion aftereffects (MAEs) and the kinetic depth effect (KDE). To test whether second-order stimuli support computations relating to motion-in-depth we examined the vection illusion (illusory self motion induced by image flow) using a vection stimulus (V, expanding concentric rings) that depicted a linear path through a circular tunnel. The set of vection stimuli contained differing amounts of first- and second-order motion energy (ME). Subjects reported the duration of the perceived MAEs and the duration of their vection percept. In Experiment 1 both MAEs and vection durations were longest when the first-order (Fourier) components of V were present in the stimulus. In Experiment 2, V was multiplicatively combined with static noise carriers having different check sizes. The amount of first-order ME associated with V increases with check size. MAEs were found to increase with check size but vection durations were unaffected. In general MAEs depend on the amount of first-order ME present in the signal. Vection, on the other hand, appears to depend on a representation of image flow that combines first- and second-order ME.

Humans↗
PubMed1999

Optimal spatial frequencies for discrimination of motion direction in optic flow patterns.

Spatial frequency tuning functions were measured for direction discrimination of optic flow patterns. Three subjects discriminated the direction of a curved motion path using computer generated optic flow patterns composed of randomly positioned dots. Performance was measured with unfiltered patterns and with patterns that were spatially filtered across a range of spatial frequencies (center spatial frequencies of 0.4, 0.8, 1.6, 3.2, 6.4, and 9.6 c/deg). The same subjects discriminated the direction of uniform, translational motion on the fronto-parallel plane. The uniform motion patterns were also composed of randomly positioned dots, that were either unfiltered or filtered with the same spatial filters used for the optic flow patterns. The peak spatial frequency was the same for both the optic flow and uniform motion patterns. For both types of motion, a narrow band (1.5 octaves) of optimal spatial frequencies was sufficient to support the same level of performance as found with unfiltered, broadband patterns. Additional experiments demonstrated that the peak spatial frequency for the optic flow patterns varies with mean image speed in the same manner as has been reported for moving sinusoidal gratings. These findings confirm the hypothesis that the outputs of the local motion mechanisms thought to underlie the perception of uniform motion provide the inputs to, and constrain the operation of, the mechanism that processes self motion from optic flow patterns.

Computer Graphics↗
PubMed2004

Motor functions of the Broca's region.

Broca's region in the dominant cerebral hemisphere is known to mediate the production of language but also contributes to comprehension. This region evolved only in humans and is constituted of Brodmann's areas 44 and 45 in the inferior frontal gyrus. There is, however, evidence that Broca's region overlaps, at least in part, with the ventral premotor cortex. We summarize the evidence that the motor related part of Broca's area is localized in the opercular portion of the inferior frontal cortex, mainly in area 44 of Brodmann. According to our own data, there seems to be a homology between Brodmann area 44 in humans and the monkey area F5. The non-language related motor functions of Broca's region comprise complex hand movements, associative sensorimotor learning and sensorimotor integration. Brodmann's area 44 is also a part of a specialized parieto-premotor network and interacts significantly with the neighboring premotor areas.

Animals↗
PubMed1984

The radial maze performance of mice: assessing the dimensional requirements for serial order memory in animals.

Two versions of the eight-arm radial maze were used to test the working memory abilities of CD-1 mice. In an elevated open-arm radial maze, mice quickly and successfully learned the multiple-choice procedure. However, mice trained in an enclosed-arm radial maze mastered the task only by developing a kinesthetic strategy of response. When a delay was imposed between choices 4 and 5, mice in the open-arm radial maze retained high performance levels. Choice accuracy declined markedly for mice in the enclosed-arm radial maze under delay conditions. Transference of the two groups of mice between the two mazes resulted in a complete reversal of sampling strategies. Minor changes to the enclosed-arm maze and room illumination permitted mice to successfully perform in the non-egocentric manner which they exclusively employed in the open-arm maze. The results show that mice can demonstrate a working memory capacity when in an environmentally adequate radial maze, and provide evidence against the existence of nonspatial working memory ability. The discussion examines the procedural and environmental requirements for displays of working memory, and a set of hypotheses is presented which serve to integrate the working memory and cognitive mapping theories.

Animals↗
PubMed1988

Role of the area postrema in three putative measures of motion sickness in the rat.

After thermal cauterization of the area postrema in rats the absence of conditioned taste aversion to sucrose paired with lithium chloride (0.15 M, 3.3 ml/kg) was used as a pharmacologic/behavioral index of area postrema damage. In a subsequent experiment the effects of area postrema lesions on three measures proposed as species-relevant measures of motion sickness were studied, using off-vertical rotation at 150 degrees/s for either 30 or 90 min. Lesions of area postrema did not alter postrotational suppression of drinking or amount of defecation during motion. The initial acquisition of conditioned taste aversion to a novel cider vinegar solution paired with motion was not affected by lesioning of the area postrema, but these taste aversions extinguished more slowly in lesioned rats than in sham-operates or intact controls. Results are discussed in terms of proposed humoral factors which may induce motion sickness and in light of recent data on the role of the area postrema in similar measures in species possessing the complete emetic reflex.

Animals↗
PubMed1988

Conditioned taste aversion induced by motion is prevented by selective vagotomy in the rat.

The role of the vagus nerve in motion-induced conditioned taste aversion (CTA) was studied in hooded rats. Animals with complete, selective gastric vagotomy failed to form conditioned taste aversion after multiple conditioning sessions in which the conditioned stimulus (a cider vinegar solution) was drunk immediately before a 30-min exposure to vertical axis rotation at 150 degrees/s. Results are discussed with reference to the use of CTA as a measure of motion-induced "sickness" or gastrointestinal disturbance, and, because motion-induced CTA requires that both the vagus nerve and the vestibular apparatus be intact, in light of the possible convergence of vagal and vestibular functions.

Afferent Pathways↗
PubMed1989

Vestibular stimulation disrupts acquisition of place navigation in the Morris water tank task.

The significance of vestibular input for place navigation in the Morris water maze was examined in 11 hooded rats. A 5-min rotation (2 Hz) immediately preceding retrieval of an overtrained place navigation task prolonged escape latencies by about 10 s corresponding to circular swimming induced by postrotatory aftereffects, but did not otherwise interfere with target location. A 1-min rotation immediately following the acquisition trial in the working memory version of the water maze task did not deteriorate performance in the retrieval trial performed 5 min later. Two components of the acquisition trial, i.e., active search of the hidden target (up to 1 min) and latent learning during the 30-s stay on the platform, contribute almost equally to the formation of the working memory trace. A 1-min rotation immediately preceding the isolated platform learning component impaired subsequent retrieval but was ineffective when applied 3 min earlier. Latent learning was completely disrupted when the platform with the animal was rotated during the entire 30-s stay on the target platform or when the 30-s stay on the stationary platform was followed 0 or 3 min later by a 30-s rotation on the platform. The interfering effect of the latter procedure was suppressed by covering the platform with the animal by an opaque cylinder. It is concluded that vestibular cues are particularly important for the orientation of the animal in the gravitation field and for the estimation of the angles between vectors plotted from the animal toward external landmarks. Agreement between vestibular and visual signals is a prerequisite of efficient navigation.

Animals↗
PubMed2001

Phase and amplitude analysis in time-frequency space--application to voluntary finger movement.

Two methods operating in time-frequency space were applied to analysis of EEG activity accompanying voluntary finger movements. The first one, based on matching pursuit approach provided high-resolution distributions of power in time-frequency space. The phenomena of event related desynchronization (ERD) and synchronization (ERS) were investigated without the need of band-pass filtering. Time evolution of mu- and beta-components was observed in a detailed way. The second method was based on a multichannel autoregressive model (MVAR) adapted for investigation of short-time changes in EEG signal. The direction and spectral content of the EEG activity propagation was estimated by means of short-time directed transfer function (SDTF). The evidence of 'cross-talk' between different areas of motor and sensory cortex was found. The earlier known phenomena, connected with voluntary movements, were confirmed and a new evidence concerning focal ERD/surround ERS and beta activity post-movement synchronization was found.

Algorithms↗
PubMed2000

Motor learning and Parkinson's disease: refinement of within-limb and between-limb coordination as a result of practice.

Even though the basal ganglia have been assigned a role in motor learning, few studies have addressed motor learning capabilities in Parkinson patients. In the present experiment, improvement of bimanual figure drawing across practice was compared between Parkinson patients and normal age-matched controls. At regular intervals during acquisition, performance was assessed under normal vision and blindfolded conditions. At initiation of practice, the typical signs associated with Parkinson's disease became evident, such as bradykinesia and hypometria. Moreover, reduced synchronization between the force-time specifications of both limbs was observed. When vision was withdrawn, Parkinson patients showed a larger drift of drawing performance across the workspace, indicative of a decline in proprioception. In spite of the aforementioned deficits, Parkinson patients made marked improvements in the speed of execution, the consistency of the spatial trajectories, and the synchronization between the limbs across practice, even though they never reached the performance levels obtained in elderly controls. The findings demonstrate that Parkinson patients do benefit from practice to refine their upper limb control and to alleviate their most basic motor deficits.

Aged↗
PubMed2003

Visuomotor deficits and fast recovery after area V6A lesion in monkeys.

In order to study the involvement of area V6A in visually guided behavior, restricted lesions to the anterior bank of the parieto-occipital sulcus (POs) were made in two adult Cercopithecus aethiops monkeys, trained in visuomotor tests. Beside the known clinical signs of parietal deficit (abnormal posture of the arm contralateral to the most recent lesion and reluctance to use it), misreaching was evident soon after surgery and disappeared quickly. Uncertainties in a landmark test and prolonged response times to the pressing of light-buttons lasted for a few weeks and 1 month, respectively. As suggested by previous anatomical and physiological data, these findings confirm the role of the POs region in the execution of reaching movements. Moreover, they also demonstrate that following lesion, locally networked areas can rapidly adjust in order to re-establish pre-lesional behavior. These adjustments take place well before that any anatomical changes may occur.

Animals↗
PubMed2002

Processing of tactile and kinesthetic signals from bilateral sides of the body in the postcentral gyrus of awake monkeys.

Earlier studies pointed out that in the primary somatosensory cortex (SI) the receptive fields (RF) of bilateral neurons were related exclusively to the body midline. We recently found a substantial number of neurons with bilateral RFs on hand digits, shoulders/arms or legs/feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake macaque monkeys. The RFs of these neurons were generally of the most complex types found in this region of the cortex, and thus they were considered to be at the highest level along the hierarchical chain of information processing. We conclude that there are two types of bilateral RFs in the postcentral gyrus, one representing the midline structures such as the intraoral cavity, chin or trunk and the other related to limb structures such as fingers, hands, arms, shoulders, legs and girdles. Functional significance of the bilateral activity could be understood in behavioral context as it is seen more extensively in the body parts where bilateral coordination is essential.

Animals↗
PubMed2002

Synaptic transmission between single tactile and kinaesthetic sensory nerve fibers and their central target neurones.

Selective activation of single tactile or kinaesthetic afferent nerve fibers in conscious human subjects by means of the intraneural microstimulation procedure reveals quite marked differences among the different classes in their capacity for eliciting perceptual responses. This work, conducted largely by Swedish researchers, suggests that there may be differential transmission security for different fiber classes across synaptic linkages in the central tactile and kinaesthetic sensory pathways. In order to test this hypothesis we have developed an experimental paradigm in the anaesthetized cat, based upon paired, simultaneous recording from an individual afferent fiber in an intact peripheral nerve fascicle, and from the central target neurone of that afferent fiber within the dorsal column nuclei (DCN). Our results demonstrate, for all tactile and kinaesthetic fiber classes examined, that the minimum sensory input, a single impulse in one sensory fiber, can generate spike output from DCN target neurones. This remarkable security of transmission has been demonstrated for single Pacinian corpuscle (PC) fibers (associated with Pacinian Corpuscle receptors); single SAI and SAII fibers (the slowly adapting Type I and II tactile fibers associated, respectively, with Merkel and Ruffini receptor endings); the Hair Follicle Afferent fibers (HFA fibers); and kinaesthetic afferent fibers of both joint and muscle origin. The results demonstrate that the differential capacities of various tactile and kinaesthetic fiber classes to generate perceptual responses when activated singly in microneurography experiments do not appear to be explicable in terms of systematic differences in DCN transmission characteristics.

Animals↗