Stimulus Intensity

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Feliks Jaroszyk - One of the best experts on this subject based on the ideXlab platform.

C. Bonnet - One of the best experts on this subject based on the ideXlab platform.

  • On the relation between Stimulus Intensity and processing time: Piéron's law and choice reaction time.
    Perception and Psychophysics, 1996
    Co-Authors: D. Pins, C. Bonnet
    Abstract:

    Pi?n (1914, 1920, 1952) demonstrated that simple reaction time (SRT) decays as a hyperbolic function of luminance in detection tasks. However, whether such a relationship holds equally for choice reaction time (CRT) has been questioned (Luce, 1986; Nissen, 1977), at least when the task is not brightness discrimination. In two SRT and three CRT experiments, we investigated the function that relates reaction time (RT) to Stimulus Intensity for five levels of luminance covering the entire mesopic range. The psychophysical experiments consisted of simple detection, two-alternative forced choice (2 AFC) with spatial uncertainty, 2 AFC with semantic categorization, and 2 AFC with orientation discrimination. The results of the experiments showed that mean RT increases with task complexity. However, the exponents of the functions relating RT to Stimulus Intensity were found to be similar in the different experiments. This finding indicates that Pi?n's law holds for CRT as well as for SRT. It describes RT as a power function of Stimulus Intensity, with similar exponents, regardless of the complexity of the task.

  • on the relation between Stimulus Intensity and processing time pieron s law and choice reaction time
    Attention Perception & Psychophysics, 1996
    Co-Authors: D. Pins, C. Bonnet
    Abstract:

    Pieron (1914, 1920, 1952) demonstrated that simple reaction time (SRT) decays as a hyperbolic function of luminance in detection tasks. However, whether such a relationship holds equally for choice reaction time (CRT) has been questioned (Luce, 1986; Nissen, 1977), at least when the task is not brightness discrimination. In two SRT and three CRT experiments, we investigated the function that relates reaction time (RT) to Stimulus Intensity for five levels of luminance covering the entire mesopic range. The psychophysical experiments consisted of simple detection, two-alternative forced choice (2 AFC) with spatial uncertainty, 2 AFC with semantic categorization, and 2 AFC with orientation discrimination. The results of the experiments showed that mean RT increases with task complexity. However, the exponents of the functions relating RT to Stimulus Intensity were found to be similar in the different experiments. This finding indicates that Pieron’s law holds for CRT as well as for SRT. It describes RT as a power function of Stimulus Intensity, with similar exponents, regardless of the complexity of the task.

Douglas P Munoz - One of the best experts on this subject based on the ideXlab platform.

  • Stimulus Intensity modifies saccadic reaction time and visual response latency in the superior colliculus
    Experimental Brain Research, 2006
    Co-Authors: Andrew H Bell, M A Meredith, A J Van Opstal, Douglas P Munoz
    Abstract:

    Performance in a reaction time task can be strongly influenced by the physical properties of the stimuli used (e.g., position and Intensity). The reduction in reaction time observed with higher-Intensity visual stimuli has been suggested to arise from reduced processing time along the visual pathway. If this hypothesis is correct, activity should be registered in neurons sooner for higher-Intensity stimuli. We evaluated this hypothesis by measuring the onset of neural activity in the intermediate layers of the superior colliculus while monkeys generated saccades to high or low-Intensity visual stimuli. When Stimulus Intensity was high, the response onset latency was significantly reduced compared to low-Intensity stimuli. As a result, the minimum time for visually triggered saccades was reduced, accounting for the shorter saccadic reaction times (SRTs) observed following high-Intensity stimuli. Our results establish a link between changes in neural activity related to Stimulus Intensity and changes to SRTs, which supports the hypothesis that shorter SRTs with higher-Intensity stimuli are due to reduced processing time.

Anthony N. Carlsen - One of the best experts on this subject based on the ideXlab platform.

  • Increased auditory Stimulus Intensity results in an earlier and faster rise in corticospinal excitability.
    Brain research, 2019
    Co-Authors: Laura St Germain, Victoria Smith, Dana Maslovat, Anthony N. Carlsen
    Abstract:

    Abstract Increasing the Intensity of auditory stimuli has been shown to produce faster simple reaction times (RTs). Typical explanations for this effect involve earlier detection of the more intense Stimulus; however, these explanations fail to consider how Stimulus Intensity may impact response initiation processing. To investigate the mechanism responsible for the auditory Stimulus Intensity effect, transcranial magnetic stimulation (TMS) was applied at various times during the simple RT interval (equivalent to 0, 30, 45, 60, and 75% of baseline RT) to examine changes in corticospinal excitability after a go-signal of varying Intensity (60, 70, 80, or 90 dB). Premotor RT data confirmed a Stimulus Intensity effect whereby the 90 dB Stimulus resulted in faster RTs than all other intensities. Analysis of motor evoked potential (MEP) amplitude elicited by TMS across Stimulus Intensity conditions revealed that in the 80 dB and 90 dB conditions, corticospinal excitability began to increase earlier from baseline (pre-Stimulus) levels, supporting the detection hypothesis. In addition, MEP amplitude increased at a greater rate during the RT interval for the 90 dB condition, indicative of impacts on response initiation. These results indicate that Stimulus Intensity effects result from a combination of earlier detection and faster initiation.

  • Increases in Stimulus Intensity lead to a greater rate of activation accumulation in primary motor cortex
    2018
    Co-Authors: Laura St Germain, Victoria Smith, Dana Maslovat, Anthony N. Carlsen
    Abstract:

    The Stimulus Intensity effect is a phenomenon whereby in a simple reaction time (RT) task, as the go-signal Stimulus Intensity increases (e.g., brighter, louder), RT decreases. While the Stimulus Intensity effect is highly robust, it is unclear how response initiation processes are affected by the more intense stimuli. To investigate the neural processes underlying Stimulus Intensity effects, participants (n=14) completed a simple RT task requiring targeted wrist extension in response to an acoustic Stimulus of 60, 70, 80, or 90dB. On each trial transcranial magnetic stimulation (TMS) was applied (110% of resting threshold) over the wrist extensor representation of the primary motor cortex (M1) at 0, 30, 45, 60, and 75% of each participant's respective baseline RT (determined from a block of 10 trials with an 80dB go-signal). Results confirmed a Stimulus Intensity effect, whereby the 90dB Stimulus resulted in faster RTs than all other intensities (p=.025). Analysis of motor evoked potential (MEP) amplitude elicited by TMS revealed an Intensity by time interaction (p=.003). While all MEP amplitudes increased in size as TMS was presented later in the RT interval, the 90dB Stimulus elicited drastically larger MEP amplitudes than all other intensities when delivered at the latest time point (75% of baseline RT). These results show that M1 excitability for the 90dB Stimulus rapidly increases just prior to response onset, demonstrating that the Stimulus Intensity effect may occur due to a faster rate of increase in M1 activation levels prior to response execution for louder stimuli.Acknowledgments: Supported by NSERC and the Ontario Ministry of Research and Innovation and Science.

  • Startle produces early response latencies that are distinct from Stimulus Intensity effects
    Experimental Brain Research, 2007
    Co-Authors: Anthony N. Carlsen, Chris J. Dakin, Romeo Chua, Ian M. Franks
    Abstract:

    Recent experiments pairing a startling Stimulus with a simple reaction time (RT) task have shown that when participants are startled, a prepared movement was initiated earlier in comparison to voluntary initiation. It has been argued that the startle acts to trigger the response involuntarily. However, an alternative explanation is that the decrease in RT may be due to Stimulus Intensity effects, not involuntary triggering. Thus the aim of the current investigation was to determine if RT simply declined in a linear fashion with increasing Stimulus Intensity, or if there was a point at which RT dramatically decreased. In the present experiment participants completed 50 active wrist extension trials to a target in response to an auditory Stimulus of varying Stimulus Intensity (83–123 dB). The presented data show that RTs associated with a startle response are separate from Stimulus Intensity facilitated responses. Furthermore, this startle facilitation is more highly associated with sternocleidomastoid electromyographic (EMG) activity, rather than the EMG from the widely used startle response indicator muscle orbicularis oculi.

Piotr Jaskownki - One of the best experts on this subject based on the ideXlab platform.

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