Speeded detection of spectrotemporal modulations of sound

We tested whether joint spectrotemporal sensitivity follows from spectrotemporal separability for normal-hearing conditions and for impaired-hearing simulations. In a manual reaction-time task, normal-hearing listeners had to detect the onset of a ripple (with density between 0-8 cycles/octave and a fixed modulation depth of 50%), that moved up or down the log-frequency axis at constant velocity (between 0-64 Hz), in an otherwise-unmodulated broadband white-noise. Spectral and temporal modulations elicited band-pass filtered sensitivity characteristics, with fastest detection rates around 1 cycle/oct and 32 Hz for normal-hearing conditions. These results closely resemble data from other studies that typically used the modulation-depth threshold as a sensitivity measure for spectral-temporal modulations. To simulate hearing-impairment, stimuli were processed with a 6-channel cochlear-implant vocoder, and a hearing-aid simulation that introduced spectral smearing and low-pass filtering. Reaction times were always much slower compared to normal hearing, especially for the highest spectral densities. Binaural performance was predicted well by the benchmark race model of statistical facilitation of independent monaural channels. For the impaired-hearing simulations this implied a "best-of-both-worlds" principle in which the listeners relied on the hearing-aid ear to detect spectral modulations, and on the cochlear-implant ear for temporal-modulation detection. Although singular-value decomposition indicated that the joint spectrotemporal sensitivity matrix could be largely reconstructed from independent temporal and spectral sensitivity functions, in line with time-spectrum separability, a significant inseparable spectral-temporal interaction was present in all hearing conditions. These results imply that the reaction-time task yields a solid and effective objective measure of acoustic spectrotemporal modulation sensitivity, which may also be applicable to hearing-impaired individuals.

Frontal-Sensory Cortical Projections Become Dispensable for Attentional Performance Upon a Reduction of Task Demand in Mice

Top-down attention is a dynamic cognitive process that facilitates the detection of the task-relevant stimuli from our complex sensory environment. A neural mechanism capable of deployment under specific task-demand conditions would be crucial to efficiently control attentional processes and improve promote goal-directed attention performance during fluctuating attentional demand. Previous studies have shown that frontal top-down neurons projecting from the anterior cingulate area (ACA) to the visual cortex (VIS; ACAVIS) are required for visual attentional behavior during the 5-choice serial reaction time task (5CSRTT) in mice. However, it is unknown whether the contribution of these projecting neurons is dependent on the extent of task demand. Here, we first examined how behavior outcomes depend on the number of locations for mice to pay attention and touch for successful performance, and found that the 2-choice serial reaction time task (2CSRTT) is less task demanding than the 5CSRTT. We then employed optogenetics to demonstrate that suppression ACAVIS projections immediately before stimulus presentation has no effect during the 2CSRTT in contrast to the impaired performance during the 5CSRTT. These results suggest that ACAVIS projections are necessary when task demand is high, but once a task demand is lowered, ACAVIS neuron activity becomes dispensable to adjust attentional performance. These findings support a model that the frontal-sensory ACAVIS projection regulates visual attention behavior during specific high task demand conditions, pointing to a flexible circuit-based mechanism for promoting attentional behavior.

High Gamma and Beta Temporal Interference Stimulation in the Human Motor Cortex Improves Motor Functions

Background: Temporal interference (TI) stimulation is a new technique of non-invasive brain stimulation. Envelope-modulated waveforms with two high-frequency carriers can activate neurons in target brain regions without stimulating the overlying cortex, which has been validated in mouse brains. However, whether TI stimulation can work on the human brain has not been elucidated.Objective: To assess the effectiveness of the envelope-modulated waveform of TI stimulation on the human primary motor cortex (M1).Methods: Participants attended three sessions of 30-min TI stimulation during a random reaction time task (RRTT) or a serial reaction time task (SRTT). Motor cortex excitability was measured before and after TI stimulation.Results: In the RRTT experiment, only 70 Hz TI stimulation had a promoting effect on the reaction time (RT) performance and excitability of the motor cortex compared to sham stimulation. Meanwhile, compared with the sham condition, only 20 Hz TI stimulation significantly facilitated motor learning in the SRTT experiment, which was significantly positively correlated with the increase in motor evoked potential.Conclusion: These results indicate that the envelope-modulated waveform of TI stimulation has a significant promoting effect on human motor functions, experimentally suggesting the effectiveness of TI stimulation in humans for the first time and paving the way for further explorations.

Perceived Timing of Cutaneous Vibration and Intracortical Microstimulation of Human Somatosensory Cortex

BackgroundElectrically stimulating the somatosensory cortex can partially restore the sense of touch. Though this technique bypasses much of the neuroaxis, prior studies with non-human primates have found that conscious detection of touch elicited by intracortical microstimulation (ICMS) lags behind the detection of vibration applied to the skin. These findings may have been influenced by a mismatch in stimulus intensity; typically, vibration is perceived as more intense than ICMS, which can significantly impact temporal perception.ObjectiveThe goal of this study was to evaluate the relative latency at which intensity-matched vibration and ICMS are perceived in a human subject.MethodsA human participant implanted with microelectrode arrays in somatosensory cortex performed a reaction time task and a temporal order judgment (TOJ) task. In the reaction time task, the participant was presented with ICMS or vibration and verbal response times were obtained. In the TOJ task, the participant was sequentially presented with a pair of stimuli – ICMS followed by vibration or vice versa – and reported which stimulus occurred first.ResultsWhen ICMS and vibration were matched in perceived intensity, the reaction time to vibration was ∼50 ms faster than ICMS. However, in the TOJ task, ICMS and vibratory sensations arose at comparable latencies, with points of subjective simultaneity that were not significantly different from zero.ConclusionsBecause the perception of ICMS is slower than that of intensity-matched vibration, it may be necessary to stimulate at stronger ICMS intensities (thus decreasing reaction time) when incorporating ICMS sensory feedback into neural prostheses.

The interplay between unexpected events and behavior in the development of explicit knowledge in implicit sequence learning

Some studies in implicit learning investigate the mechanisms by which implicitly acquired knowledge (e.g., learning a sequence of responses) becomes consciously aware. It has been suggested that unexpected changes in the own behavior can trigger search processes, of which the outcome then becomes aware. A consistent empirical finding is that participants who develop explicit knowledge show a sudden decrease in reaction times, when responding to sequential events. This so called RT-drop might indicate the point of time when explicit knowledge occurs. We investigated whether an RT-drop is a precursor for the development of explicit knowledge or the consequence of explicit knowledge. To answer this question, we manipulated in a serial reaction time task the timing of long and short stimulus-onset asynchronies (SOA). For some participants, the different SOAs were presented in blocks of either long or short SOAs, while for others, the SOAs changed randomly. We expected the participants who were given a blocked presentation to express an RT-drop because of the predictable timing. In contrast, randomly changing SOAs should hamper the expression of an RT-drop. We found that more participants in the blocked-SOA condition than in the random-SOA condition showed an RT-drop. Furthermore, the amount of explicit knowledge did not differ between the two conditions. The findings suggest that the RT-drop does not seem to be a presupposition to develop explicit knowledge. Rather, it seems that the RT-drop indicates a behavioral strategy shift as a consequence of explicit knowledge.

Specific Cues Can Improve Procedural Learning and Retention in Developmental Coordination Disorder and/or Developmental Dyslexia

The present study investigates procedural learning of motor sequences in children with developmental coordination disorder (DCD) and/or developmental dyslexia (DD), typically-developing children (TD) and healthy adults with a special emphasis on (1) the role of the nature of stimuli and (2) the neuropsychological functions associated to final performance of the sequence. Seventy children and ten adults participated in this study and were separated in five experimental groups: TD, DCD, DD, and DCD + DD children and adults. Procedural learning was assessed with a serial reaction time task (SRTT) that required to tap on a specific key as accurately and quickly as possible when stimuli appeared on the screen. Three types of stimuli were proposed as cues: the classical version of the SRTT with 4 squares aligned horizontally on the screen, giving visuospatial cues (VS cues), and two modified versions, with 4 letters aligned horizontally on the screen (VS + L cues) and letters at the center of the screen (L cues). Reaction times (RT) during the repeated and random blocks allowed assessing three phases of learning: global learning, specific learning and retention of the sequence. Learning was considered as completed when RT evolved significantly in the three phases. Neuropsychological assessment involved, among other functions, memory and attentional functions. Our main result was that learning and retention were not influenced by the available cues in adults whereas learning improved with specific cues in children with or without neurodevelopmental disorders. More precisely, learning was not completed with L cues in children with neurodevelopmental disorders. For children with DD, learning was completed with the VS and VS + L cues whereas for children with DCD (with or without DD), learning was completed with combined VS + L cues. Comorbidity between DD and DCD had no more impact on procedural learning than DCD alone. These results suggest that learning depends on the nature of cues available during practice and that cues allowing learning and retention depend on the type of disorder. Moreover, selective attention was correlated with RT during retention, suggesting that this neuropsychological function is important for procedural learning whatever the available cues.

Response triggering by an acoustic stimulus increases with stimulus intensity and is best predicted by startle reflex activation

In a simple reaction time task, the presentation of a startling acoustic stimulus has been shown to trigger the prepared response at short latency, known as the StartReact effect. However, it is unclear under what conditions it can be assumed that the loud stimulus results in response triggering. The purpose of the present study was to examine how auditory stimulus intensity and preparation level affect the probability of involuntary response triggering and the incidence of activation in the startle reflex indicator of sternocleidomastoid (SCM). In two reaction time experiments, participants were presented with an irrelevant auditory stimulus of varying intensities at various time points prior to the visual go-signal. Responses were independently categorized as responding to either the auditory or visual stimulus and those with or without SCM activation (i.e., SCM+/−). Both the incidence of response triggering and proportion of SCM+ trials increased with stimulus intensity and presentation closer to the go-signal. Data also showed that participants reacted to the auditory stimulus at a much higher rate on trials where the auditory stimulus elicited SCM activity versus those that did not, and a logistic regression analysis confirmed that SCM activation is a reliable predictor of response triggering for all conditions.

Metaphors’ effect on off-line cognition: A preliminary study based on a reaction time task

The modality of apprehension and processing of metaphorical expressions in comparison with non-metaphorical ones has hitherto captivated numerous researchers in manifold fields of study, such as linguistics, psychology, and cognitive sciences. More specially, metaphors used in a one-sentence paragraph have been the subjects of many studies. However, cognitive functions of structural metaphors haven’t been entirely noteworthy in contrast with non-metaphorical expressions employed in textual context. In this study, the interrelationship between memory and conceptual metaphor in significant cognitive processes has been examined in a textual context. In this respect, the hypothesis, that conceptual metaphor as a value can assist with the recognition and recollection process and incorporate the quintessence of our cerebrations, has been put to test. To evaluate this assumption, the reaction time task is used. Each testable case has been subjected to analysis within two analogous contexts, in a metaphorical and non-metaphorical manner. Afterwards, terms were displayed, and the subjects needed to determine as swiftly as possible whether these vocabularies were exemplified or not. The results indicated that the terms pertaining to the schema and other terms included in metaphorical context would be processed faster than the one with non-metaphorical context. With regard to the obtained data, it seems that the conceptual metaphor generates semantic networks in the mind which will be more accessible to memory upon information retrieval.

Biased memory retrieval in the service of shared reality with an audience: The role of cognitive accessibility

After communicators have tuned a message about a target person’s behaviors to their audience’s attitude, their recall of the target’s behaviors is often evaluatively consistent with their audience’s attitude. This audience-tuning effect on recall has been explained as resulting from the communicators’ creation of a shared reality with the audience, which helps communicators to achieve epistemic needs for confident judgments and knowledge. Drawing on the ROAR (Relevance Of A Representation) model, we argue that shared reality increases the cognitive accessibility of information consistent (vs. inconsistent) with the audience’s attitude, due to enhanced truth relevance of this information. We tested this prediction with a novel reaction-time task in three experiments employing the saying-is-believing paradigm. Faster reactions to audience-consistent (vs. audience-inconsistent) information were found for trait information but not for behavioral information. Thus, audience-congruent accessibility bias emerged at the level at which impressions and judgments of other persons are typically organized. Consistent with a shared-reality account, the audience-consistent accessibility bias was correlated with perceived shared reality about the target person and with epistemic trust in the audience. Among possible explanations, the findings are best reconciled with the view that the creation of shared reality with an audience triggers basic and "automatic" (spontaneous, low-level) cognitive mechanisms that facilitate the retrieval of audience-congruent (vs. audience-incongruent) trait information about a target person.