Stimulus Speed Research Articles

Representation of motion onset and offset in an augmented Barlow-Levick model of motion detection

Kinetic occlusion produces discontinuities in the optic flow field, whose perception requires the detection of an unexpected onset or offset of otherwise predictably moving or stationary contrast patches. Many cells in primate visual cortex are directionally selective for moving contrasts, and recent reports suggest that this selectivity arises through the inhibition of contrast signals moving in the cells’ null direction, as in the rabbit retina. This nulling inhibition circuit (Barlow-Levick) is here extended to also detect motion onsets and offsets. The selectivity of extended circuit units, measured as a peak evidence accumulation response to motion onset/offset compared to the peak response to constant motion, is analyzed as a function of stimulus speed. Model onset cells are quiet during constant motion, but model offset cells activate during constant motion at slow speeds. Consequently, model offset cell speed tuning is biased towards higher speeds than onset cell tuning, similarly to the speed tuning of cells in the middle temporal area when exposed to speed ramps. Given a population of neurons with different preferred speeds, this asymmetry addresses a behavioral paradox—why human subjects in a simple reaction time task respond more slowly to motion offsets than onsets for low speeds, even though monkey neuron firing rates react more quickly to the offset of a preferred stimulus than to its onset.

Effects of Temporal Features and Order on the Apparent duration of a Visual Stimulus

The apparent duration of a visual stimulus has been shown to be influenced by its speed. For low speeds, apparent duration increases linearly with stimulus speed. This effect has been ascribed to the number of changes that occur within a visual interval. Accordingly, a higher number of changes should produce an increase in apparent duration. In order to test this prediction, we asked subjects to compare the relative duration of a 10-Hz drifting comparison stimulus with a standard stimulus that contained a different number of changes in different conditions. The standard could be static, drifting at 10 Hz, or mixed (a combination of variable duration static and drifting intervals). In this last condition the number of changes was intermediate between the static and the continuously drifting stimulus. For all standard durations, the mixed stimulus looked significantly compressed (∼20% reduction) relative to the drifting stimulus. However, no difference emerged between the static (that contained no changes) and the mixed stimuli (which contained an intermediate number of changes). We also observed that when the standard was displayed first, it appeared compressed relative to when it was displayed second with a magnitude that depended on standard duration. These results are at odds with a model of time perception that simply reflects the number of temporal features within an interval in determining the perceived passing of time.

Visual and spatial modulation of tactile extinction: behavioural and electrophysiological evidence

Crossing the hands over the midline reduces left tactile extinction to double simultaneous stimulation in right-brain-damaged patients, suggesting that spatial attentional biases toward the ipsilesional (right) side of space contribute to the patients' contralesional (left) deficit. We investigated (1) whether the position of the left hand, and its vision, affected processing speed of tactile stimuli, and (2) the electrophysiological underpinnings of the effect of hand position. (1) Four right-brain-damaged patients with spatial neglect and contralesional left tactile extinction or somatosensory deficits, and eight neurologically unimpaired participants, performed a speeded detection task on single taps delivered on their left index finger. In patients, placing the left hand in the right (heteronymous) hemi-space resulted in faster reaction times (RTs) to tactile stimuli, compared to placing that hand in the left (homonymous) hemi-space, particularly when the hand was visible. By contrast, in controls placing the left hand in the heteronymous hemi-space increased RTs. (2) Somatosensory event-related potentials (ERPs) were recorded from one patient and two controls in response to the stimulation of the left hand, placed in the two spatial positions. In the patient, the somatosensory P70, N140, and N250 components were enhanced when the left hand was placed in the heteronymous hemi-space, whereas in controls these components were not modulated by hand position. The novel findings are that in patients placing the left hand in the right, ipsilesional hemi-space yields a temporal advantage in processing tactile stimuli, and this effect may rely on a modulation of stimulus processing taking place as early as in the primary somatosensory cortex, as indexed by evoked potentials. Furthermore, vision enhances tactile processing specifically when the left hand is placed in the hemi-space toward which the patients' attentional biases are pathologically directed, namely rightwards.

The Effects of Integrated Visual and Auditory Stimulus Speed on Gait of Individuals with Stroke

The Effects of Integrated Visual and Auditory Stimulus Speed on Gait of Individuals with Stroke

Mice mechanoreceptors are modulated by Cav3.2 T‐type calcium channels

Mechanoreceptors are sensory receptors that respond to mechanical displacement and provide the senses of touch, pressure, vibration and proprioception. Mice have three types of low-threshold mechanoreceptors: slowly adapting mechanoreceptors (SAMs), rapidly adapting mechanoreceptors (RAMs) and D-hair receptors (Driscoll & Tavernarakis, 2000). D-hair receptors are the end-terminal of type Aδ fibre axons and present a high sensitivity and ultra-rapid temporal detection of slowly moving stimuli. The mRNA expression for the T-type voltage-gated calcium channel Cav3.2 is the only marker defined for mechanoreceptors and found almost exclusively in D-hair receptors. The Cav3.2 gene encodes one of the three low-voltage-activated (LVA) Ca2+ channels (Cav3.1, Cav3.2 and Cav3.3) and are all expressed by sensory neurons in the DRG (Iftinca et al. 2007). Previous published studies proposed that Cav3.2 channel has a primary role in nociception (Bourinet et al. 2005). However, another research group that used miberfradil, a drug that blocks all T-type channels, suggested that the mechanosensitivity of D-hair receptors is reduced by blockade of LVA channels (Shin et al. 2003). For this reason the specific physiological properties of the Cav3.2 channel has not been accurately described. In a recent issue of The Journal of Physiology, Wang & Lewin (2011) conducted a study with the purpose of demonstrating the role of the T-type Cav3.2 channels. In this study, Cav3.2−/− mutant mice were used to directly address the role of this channel in sensory transduction of cutaneous mechanoreceptors and nociceptors. Mice were produced by gene targeting in mouse ES cells; the targeting vector was designed to delete the IS5 region of the murine Cacna1H gene, which resulted in deletion of exon 6, corresponding to amino acid residues 216 to 267. This method was helpful in examining the mechanosensitivity of nociceptors and mechanoreceptors in normal Cav3.2 mice and in Cav3.2−/− mutant mice, proving that nociceptors sensitivity was not altered when the Cav3.2 gene was suppressed; on the other hand, D-hair receptor sensibility was drastically impaired in their ability to encode the properties of moving stimuli, losing their high sensitivity and ability to ensure rapid temporal detection to skin movement. In addition the functional properties of other mechanoreceptors and nociceptors were unaffected by the suppression of Cav3.2 channels. Why is this important? These new data provide conclusive results of the specific function of the T-type Cav3.2 channel, solving the previous controversy about its physiological function and proving that this specific gene is responsible for providing the functional and distinctive properties of D-hair receptors. Thus, this study encloses the specific activity of this gene, being now considered not only a high specific marker of D-hair receptors but also indispensable to maintain their high sensitivity in the detection of skin deflection. The expression of Cav3.2 in D-hair mechanoreceptors may serve to provide highly accurate temporal information about rapidly changing stimuli. This information helps humans to make fast and precise judgments about the speed and direction of tactile stimuli, a characteristic that can be considered vital for survival and functionality. This is the first time that the regulation for temporal coding in mouse mechanoreceptors from Cav3.2 T-type channels has been proved. Nevertheless, results from this study showed that there exists a possibility that a minor sub-population of nociceptors is dependent on the presence of Cav3.2 channels. The research revealed no certainty that such a population exists, and it is highly unlikely that this kind of population could be identified. Further studies will be needed to ascertain if this is indeed a possibility.

Fowl communicate the size, speed and proximity of avian stimuli through graded structure in referential alarm calls

Many animals produce alarm calls that warn conspecifics about predators. In some species, alarm calls communicate continuous traits associated with a predator encounter, such as its level of threat. In other species, alarm calls communicate categorical traits, such as predator class (e.g. avian versus terrestrial), and are consequently considered functionally referential. In theory, functionally referential alarm calls can simultaneously communicate continuously distributed traits, though examples of such calls are rare. Such dual-function calls could be adaptive because they would enable receivers to tailor their responses to a specific predator class, as well as to more subtle characteristics of individual attacks. Here, we tested whether male fowl (Gallus gallus) communicate continuous variation in avian stimuli through graded structure in their functionally referential aerial alarm calls. In the first experiment, we held male fowl in an indoor test cage and allowed them to view wild birds flying past a window. We recorded their alarm calls and compared the structure to the size, speed, and proximity of the eliciting stimuli. Stimuli that appeared closer, larger, and faster elicited alarm calls that were shorter, louder, clearer, and lower in frequency. In the second experiment, we broadcast alarm calls to foraging females and compared their responses to the graded structural changes documented earlier. Females exhibited greater initial responses and finished feeding later in response to louder alarm calls. Together, these results show that fowl communicate the size, speed and proximity of avian stimuli through graded variation in their functionally referential aerial alarm calls.

Changing expectations about speed alters perceived motion direction

Summary Our perceptions are fundamentally altered by our knowledge of the world. When cloud-gazing, for example, we tend spontaneously to recognize known objects in the random configurations of evaporated moisture. How our brains acquire such knowledge and how it impacts our perceptions is a matter of heated discussion. A topic of recent debate has concerned the hypothesis that our visual system ‘assumes' that objects are static or move slowly [1] rather than more quickly [1–3]. This hypothesis, or ‘prior on slow speeds', was postulated because it could elegantly explain a number of perceptual biases observed in situations of uncertainty [2]. Interestingly, those biases affect not only the perception of speed, but also the direction of motion. For example, the direction of a line whose endpoints are hidden (as in the ‘aperture problem') or poorly visible (for example, at low contrast or for short presentations) is more often perceived as being perpendicular to the line than it really is — an illusion consistent with expecting that the line moves more slowly than it really does. How this ‘prior on slow speeds' is shaped by experience and whether it remains malleable in adults is unclear. Here, we show that systematic exposure to high-speed stimuli can lead to a reversal of this direction illusion. This suggests that the shaping of the brain's prior expectations of even the most basic properties of the environment is a continuous process.

Efeito da velocidade do estímulo no desempenho de uma tarefa de antecipação-coincidência em destros e canhotos

Destros e canhotos diferem quando comparados em algumas tarefas motoras, parecendo os canhotos usufruir de alguma vantagem em tarefas visuo-motoras. Neste estudo foi analisado, em cada grupo de preferência manual, o efeito da velocidade do estímulo, do sexo e da mão de execução no desempenho de uma tarefa simples de antecipação-coincidência. Participaram 12 destros e 12 canhotos de ambos os sexos, estudantes universitários de Desporto. Empregou-se o "Bassin Anticipation Timer" para avaliar a capacidade de antecipação-coincidência em três velocidades: 268 cm/s, 402,3 cm/s e 536,4 cm/s (6, 9 e 12 mph, respectivamente). Os sujeitos executaram a tarefa tanto com a mão preferida como com a mão não preferida. Principais resultados: 1) apenas os destros foram afetados pela variável velocidade do estímulo, apresentando antecipação das respostas e maior variabilidade na velocidade 268 cm/s, enquanto nas velocidades 402,3 cm/s e 536,4 cm/s as respostas foram enviesadas no sentido do atraso da resposta e com variabilidade menos acentuada na velocidade mais alta; 2) o sexo teve um efeito significativo apenas nos canhotos, sendo o sexo masculino mais preciso e menos enviesado nas suas respostas do que o sexo feminino; 3) a assimetria manual manifestou-se apenas nos canhotos na velocidade de 268 cm/s e no Erro Variável. Concluímos que cada grupo de preferência manual parece comportar-se de forma diferenciada em tarefas perceptivas de Antecipação-Coincidência onde a velocidade do estímulo é manipulada.

Effect of high velocity, large amplitude stimuli on the spread of depolarization in S1 “barrel” cortex

We examined the effect of large, controlled whisker movements, delivered at a high speed, on the amplitude and spread of depolarization in the anesthetized mouse barrel cortex. The stimulus speed was varied between 1500 and 6000°/s and the extent of movement was varied between 4° and 16°. The rate of rise of the response was linearly related to the rate of rise of the stimulus. The initial spatial extent of cortical activation was also related to the rate of rise of the stimulus: that is, the faster the stimulus onset, the faster the rate of rise of the response, the larger the extent of cortex activated initially. The spatial extent of the response and the rate of rise of the response were not correlated with changes in the deflection amplitude. However, slower, longer lasting stimuli produced an Off response, making the actual extent of activation larger for the slowest rising stimuli. These results indicate that the spread of cortical activation depends on stimulus features.

Invariance of firing rate and field potential dynamics to stimulus modulation rate in human auditory cortex

The effect of stimulus modulation rate on the underlying neural activity in human auditory cortex is not clear. Human studies (using both invasive and noninvasive techniques) have demonstrated that at the population level, auditory cortex follows stimulus envelope. Here we examined the effect of stimulus modulation rate by using a rare opportunity to record both spiking activity and local field potentials (LFP) in auditory cortex of patients during repeated presentations of an audio-visual movie clip presented at normal, double, and quadruple speeds. Mean firing rate during evoked activity remained the same across speeds and the temporal response profile of firing rate modulations at increased stimulus speeds was a linearly scaled version of the response during slower speeds. Additionally, stimulus induced power modulation of local field potentials in the high gamma band (64-128 Hz) exhibited similar temporal scaling as the neuronal firing rate modulations. Our data confirm and extend previous studies in humans and anesthetized animals, supporting a model in which both firing rate, and high-gamma LFP power modulations in auditory cortex follow the temporal envelope of the stimulus across different modulation rates.

BOLD responses in the superior colliculus and lateral geniculate nucleus of the rat viewing an apparent motion stimulus

In rats, the superior colliculus (SC) is a main destination for retinal ganglion cells and is an important subcortical structure for vision. Electrophysiology studies have observed that many SC neurons are highly sensitive to moving objects, but complementary non-invasive functional imaging studies with larger fields of view have been rarely conducted. In this study, BOLD fMRI is used to measure the SC and nearby lateral geniculate nucleus' (LGN) hemodynamic responses, in normal adult Sprague Dawley (SD) rats, during a dynamic visual stimulus similar to those used in long-range apparent motion studies. The stimulation paradigm consists of four light spots arranged in a linear array and turned on and off sequentially at different rates to create five effective speeds of motion (7, 14, 41, 82, and 164°/s across the visual field). Stationary periods (same light spot always on) are interleaved between the moving periods. The speed response function (SRF), the hemodynamic response amplitude at each speed tested, is measured. Significant responses are observed in the SC and LGN at all speeds. In the SC, the SRF increases monotonically from 7 to 82°/s. The minimum response amplitude occurs at 164°/s. The results suggest that the SC is sensitive to slow moving visual stimuli but the hemodynamic response is reduced at higher speeds. In the LGN, the SRF exhibits a similar trend to that of the SC, but response amplitude during 7°/s stimulation is comparable to that during 164°/s stimulation. These findings are in good agreement with previous electrophysiology studies conducted on albino rats like the SD strain. This work represents the first fMRI study of stimulus speed dependence in the SC and is also the first fMRI study of motion responsiveness in the rat.

The neural dynamics for hysteresis in visual perception

The hysteresis in the perception has been observed in many perceptual experiments, but little is known about the underlying dynamical mechanism. We simulate a visual discrimination task, as an example of hysteresis in the perception, using a spiking neuron network and the corresponding slow dynamic system. The hysteresis in visual perception has been reproduced in our simulation. We find that hysteresis is influenced by the change speed of the external stimuli and the excitatory recurrent interaction inside the selective neuron pool. The slow dynamic system reveals the dynamical mechanism underlying the hysteresis: emerging from the lag between the response of neural system and the fast change external stimuli when the slow dynamic system has a single steady state; emerging from the multiple steady states regardless of the change speed of the external stimuli. In particularly, the multiplicity of the steady state of the slow dynamic system comes from the codimension three swallowtail catastrophe which exhibits two interacting cusp catastrophes.

Conflict processing is modulated by positive emotion: ERP data from a flanker task

Recent evidence shows that negative emotional stimuli speed up the resolution of conflict between opposing response tendencies. This mechanism ensures rapid reactions in potentially threatening situations. However, it is unclear whether positive emotion has a similar effect on conflict processing. We therefore presented positive emotional words in a version of the flanker conflict task, in which conflict is elicited by incongruent target and flanker stimuli. Response times to incongruent stimuli were shortened in positive words, indicating a speeding up of conflict resolution. We also observed an enlargement of the first conflict-sensitive event-related potential (ERP) of the electroencephalogram, the N200, in positive emotional trials. The data suggest that positive emotion already modulates first stages of conflict processing. The results demonstrate that positive, reward-predicting stimuli influence conflict processing in a similar manner to threat signals. Positive emotion thus reduces the time that an organism is unable to respond due to simultaneously present conflicting action tendencies.

Sex Differences in Coincidence-Anticipation Timing (Cat): A Review

Coincidence-anticipation timing (CAT) is the ability to judge when a moving stimulus will arrive at a target. 43 articles were reviewed which investigated sex differences in this skill. Performance was typically recorded as one or more of three error measures, absolute error (AE), constant error (CE), and variable error (VE). Despite many null findings, it is argued that the evidence for a male advantage is strong, particularly for AE and VE. 10 parameters typically associated with CAT studies were analyzed (e.g., knowledge of results, number of trials, stimulus duration, and stimulus speed), but none differentiated clearly between the presence and absence of the sex difference. However, when the mean AE score was used as a measure of task difficulty, a male advantage was reliably associated with lower values of AE (easier tasks) and null findings with higher values (more difficult tasks). An attempt to compare sex difference findings from Bassin timer and real-world tasks was thwarted by the lack of studies using real-world tasks. Given little evidence for the influence of socialization on sex differences in CAT, it is suggested that the difference may have originated from the evolutionary selection of women for gathering and men for hunting.

Direction and speed tuning to visual motion in cortical areas MT and MSTd during smooth pursuit eye movements

When tracking a moving target in the natural world with pursuit eye movement, our visual system must compensate for the self-induced retinal slip of the visual features in the background to enable us to perceive their actual motion. We previously reported that the speed of the background stimulus in space is represented by dorsal medial superior temporal (MSTd) neurons in the monkey cortex, which compensate for retinal image motion resulting from eye movements when the direction of the pursuit and background motion are parallel to the preferred direction of each neuron. To further characterize the compensation observed in the MSTd responses to the background motion, we recorded single unit activities in cortical areas middle temporal (MT) and MSTd, and we selected neurons responsive to a large-field visual stimulus. We studied their responses to the large-field stimulus in the background while monkeys pursued a moving target and while fixated a stationary target. We investigated whether compensation for retinal image motion of the background depended on the speed of pursuit. We also asked whether the directional selectivity of each neuron in relation to the external world remained the same even during pursuit and whether compensation for retinal image motion occurred irrespective of the direction of the pursuit. We found that the majority of the MSTd neurons responded to the visual motion in space by compensating for the image motion on the retina resulting from the pursuit regardless of pursuit speed and direction, whereas most of the MT neurons responded in relation to the genuine retinal image motion.

Uniocular and binocular fields of rotation measures: Octopus versus Goldmann

To compare the range of ocular rotations measured by Octopus versus Goldmann perimetry. Forty subjects (20 controls and 20 patients with impaired ocular movements) were prospectively recruited, age range 21-83years. Range of uniocular rotations was measured in six vectors corresponding to extraocular muscle actions: 0°, 67°, 141°, 180°, 216°, 293°. Fields of binocular single vision were assessed at 30° intervals. Vector measurements were utilised to calculate an area score for the field of uniocular rotations or binocular field of single vision. Two test speeds were used for Octopus testing: 3°/ and 10°/second. Test duration was two thirds quicker for Octopus 10°/second than for 3°/second stimulus speed, and slightly quicker for Goldmann. Mean area for control subjects for uniocular field was 7910.45 degrees(2) for Goldmann, 7032.14 for Octopus 3°/second and 7840.66 for Octopus 10°/second. Mean area for patient subjects of right uniocular field was 8567.21 degrees(2) for Goldmann, 5906.72 for Octopus 3°/second and 8806.44 for Octopus 10°/second. Mean area for left uniocular field was 8137.49 degrees(2) for Goldmann, 8127.9 for Octopus 3°/second and 8950.54 for Octopus 10°/second. Range of measured rotation was significantly larger for Octopus 10°/second speed. Our results suggest that the Octopus perimeter is an acceptable alternative method of assessment for uniocular ductions and binocular field of single vision. Speed of stimulus significantly alters test duration for Octopus perimetry. Comparisons of results from both perimeters show that quantitative measurements differ, although qualitatively the results are similar. Differences per mean vectors were less than 5° (within clinically accepted variances) for both controls and patients when comparing Goldmann to Octopus 10°/second speed. However, differences were almost 10° for the patient group when comparing Goldmann to Octopus 3°/second speed. Thus, speed of stimulus must be considered if wishing to use these perimeters interchangeably.

道路側面に設置された点滅柱状物体により生起する視覚誘導自己運動感覚を交通工学的に応用した自動車運転者の速度感覚変化手法

We propose a method for presenting visual stimuli to change a driver's sensation of speed on a freeway: utilizing vection, one of the perceptual properties needed for self-motion and show that this method can be used on a freeway with CG simulation movies. Furthermore we investigated the relationship between the velocity of vection-inducing stimuli and the sensation of speed. Our study consists of three experiments. In all experiments, the simulated freeway 3D movies were presented on a wide hemisphere screen and the magnitude of the observer's sensation of speed was measured. Vection-inducing stimuli were produced by flickering in the boards on both sides of the freeway. This flickering yielded apparent motion. We set the speed of the vection-inducing stimuli and that of the driver's car as experimental variables. The observer compared two movies consecutively presented with different conditions and selected the one that gave a sensation of faster speed. The observer's sensation of speed increased linearly with the speed of vection-inducing stimuli. Our study suggests that controlling the speed of vection-inducing stimuli could enable the driver's sensation of speed to be manipulated in real freeways.

Exploring a Brightness-Drag Illusion

A sudden luminance increment on a moving stimulus was perceived significantly along the trajectory, in the direction of motion, from its displayed position. A nonlinear relationship with stimulus speed, for a Fröhlich-like illusion, but not for the luminance-increment illusion, challenges certain models of spatial mislocalisation and argues for different processes underlying the two illusions.

Perceived duration of Visual and Tactile Stimuli Depends on Perceived Speed

It is known that the perceived duration of visual stimuli is strongly influenced by speed: faster moving stimuli appear to last longer. To test whether this is a general property of sensory systems we asked participants to reproduce the duration of visual and tactile gratings, and visuo-tactile gratings moving at a variable speed (3.5–15 cm/s) for three different durations (400, 600, and 800 ms). For both modalities, the apparent duration of the stimulus increased strongly with stimulus speed, more so for tactile than for visual stimuli. In addition, visual stimuli were perceived to last approximately 200 ms longer than tactile stimuli. The apparent duration of visuo-tactile stimuli lay between the unimodal estimates, as the Bayesian account predicts, but the bimodal precision of the reproduction did not show the theoretical improvement. A cross-modal speed-matching task revealed that visual stimuli were perceived to move faster than tactile stimuli. To test whether the large difference in the perceived duration of visual and tactile stimuli resulted from the difference in their perceived speed, we repeated the time reproduction task with visual and tactile stimuli matched in apparent speed. This reduced, but did not completely eliminate the difference in apparent duration. These results show that for both vision and touch, perceived duration depends on speed, pointing to common strategies of time perception.

How do changes in speed affect the perception of duration?

Six experiments investigated how changes in stimulus speed influence subjective duration. Participants saw rotating or translating shapes in three conditions: constant speed, accelerating motion, and decelerating motion. The distance moved and average speed were the same in all three conditions. In temporal judgment tasks, the constant-speed objects seemed to last longer than the decelerating objects, which in turn seemed to last longer than the accelerating stimuli. In temporal reproduction tasks, the difference between accelerating and decelerating stimuli disappeared; furthermore, watching an accelerating shape lengthened the apparent duration of the subsequent (static) display. These results (a) suggest that temporal judgment and reproduction can dissociate for moving stimuli because the stimulus influences the apparent duration of the subsequent interval, and (b) constrain theories of time perception, including those which emphasize memory storage, those which emphasize the existence of a pacemaker-accumulator timing system, and those which emphasize the division of attention between temporal and non-temporal information processing.