Intensity Discrimination Task Research Articles

Processing of Facial Expressions of Emotions and Pain in Alzheimer’s Disease

Alzheimer's disease (AD) is a neurodegenerative pathology that disrupts processing of facial expressions of emotion. The impairment was demonstrated for negative emotions in tasks of matching, discriminating, and labeling facial expressions but no study has included the expression of pain in its protocol. The objective was to study the processing of emotional facial expressions in AD with a particular interest in pain expression. Twenty-seven controls, 15 mild AD patients, and 15 moderate AD patients had to perform four emotional tasks: identification of facial expressions, matching pain expressions, discriminating the intensity of pain expressions, and judging pain intensity. Some emotions were less efficiently recognized by AD patients compared to controls (p < 0.001), specifically fear from the mild stage (p < 0.05), pain and disgust from the moderate stage (p < 0.05 and p < 0.001 respectively). The Exploratory Factor Analysis showed that recognition of pain and recognition of other discreet emotions were underpinned by two different latent factors. Performances on pain expression matching task and pain intensity discrimination task did not differ by group. (p = 0.334 and p = 0.787 respectively). Finally, moderate AD patients judged the pain less intensively than the Control group for both, moderate, and severe pain intensity (p < 0.001). Our data suggest that AD disrupts the recognition of pain expression along with recognition of fear and disgust. Additionally, AD patients seem to underestimate pain intensity compared to controls. The self-rated pain scales should be adapted to the pain processing deficit of AD patients.

Identifying potential training factors in a vibrotactile P300-BCI

Brain–computer interfaces (BCI) often rely on visual stimulation and feedback. Potential end-users with impaired vision, however, cannot use these BCIs efficiently and require a non-visual alternative. Both auditory and tactile paradigms have been developed but are often not sufficiently fast or accurate. Thus, it is particularly relevant to investigate if and how users can train and improve performance. We report data from 29 healthy participants who trained with a 4-choice tactile P300-BCI during five sessions. To identify potential training factors, we pre-post assessed the robustness of the BCI performance against increased workload in a dual task condition and determined the participants’ somatosensory sensitivity thresholds with a forced-choice intensity discrimination task. Accuracy (M = 79.2% to 92.0%) and tactually evoked P300 amplitudes increased significantly, confirming successful training. Pre-post somatosensory sensitivity increased, and workload decreased significantly, but results of the dual task condition remained inconclusive. The present study confirmed the previously reported feasibility and trainability of our tactile BCI paradigm within a multi-session design. Importantly, we provide first evidence of improvement in the somatosensory system as a potential mediator for the observed training effects.

Multisensory interactions on auditory and somatosensory information in expert pianists

Fine-tuned sensory functions typically characterize skilled individuals. Although numerous studies demonstrated enhanced unimodal sensory functions at both neural and behavioral levels in skilled individuals, little is known about their multisensory interaction function, especially multisensory integration and selective attention that involve volitional control of information derived from multiple sensory organs. In the current study, expert pianists and musically untrained individuals performed five sets of intensity discrimination tasks at the auditory and somatosensory modalities with different conditions: (1) auditory stimulus, (2) somatosensory stimulus, (3) congruent auditory and somatosensory stimuli (i.e., multisensory integration), (4) auditory and task-irrelevant somatosensory stimuli, and (5) somatosensory and task-irrelevant auditory stimuli. In the fourth and fifth conditions, participants were instructed to ignore a task-irrelevant stimulus and to pay attention to a task-relevant stimulus (i.e., selective attention), respectively. While the discrimination perception was superior in the condition (3) compared to the better one of the individual unimodal conditions only in the pianists, the task-irrelevant somatosensory stimulus worsened the auditory discrimination more in the pianists than the nonmusicians. These findings indicate unique multisensory interactions in expert pianists, which enables pianists to efficiently integrate the auditory and somatosensory information, but exacerbates top-down selective inhibition of somatosensory information during auditory processing.

Cost of Dual-Task Performance in Tactile Perception Is Greater for Competing Tasks of the Same Type.

This study examines dual-task performance in the tactile modality and tests whether dual-task cost depends on task type. Experiment 1 involved competing tasks of the same type, using a primary localisation task on the left hand and a secondary localisation task on the right hand. In Experiment 2, the primary task on the left hand remained the same, while an intensity discrimination task was used as the secondary task on the right hand. Subjects in both experiments completed three conditions: the primary task alone, a dual-task condition, and the primary task with the secondary stimulus present but no response required. Across both experiments, performance on the primary task was best when it was presented alone, and there was a performance decrement when the secondary stimulus was present but not responded to. Performance on the primary task was further decreased when participants had to respond to the secondary stimulus, and the decrease was larger when the secondary task was localisation rather than discrimination. This result indicates that task type in the tactile modality may modulate the attentional cost of dual-task performance and implies partially shared resources underlie localisation and intensity discrimination.

Intensity Resolution in Individuals With Parkinson's Disease: Sensory and Auditory Memory Limitations.

Purpose The purpose of the current study was to examine sensory and auditory memory limitations on intensity resolution in individuals with Parkinson's disease as compared to healthy older and younger adults. Method Nineteen individuals with Parkinson's disease, 10 healthy age- and hearing-matched adults, and 10 healthy young adults were studied. The listeners participated in 2 intensity discrimination tasks: a lower memory load 4IAX task (sensory limitations) and a higher memory load ABX task (auditory memory limitations). Intensity resolution was examined across groups and tasks using a bias-free measurement of signal detectability known as d' (d-prime). Listeners also participated in a loudness scaling task where they were instructed to rate the loudness level of each signal intensity along the experimental continuum using a computerized 150-mm visual analog scale. Results Intensity discrimination sensitivity (d') was significantly poorer in the 4IAX and ABX conditions for the individuals with Parkinson's disease, as compared to the older and younger controls. Furthermore, a significant age-related difference was identified for the loudness scaling condition. The younger controls rated most stimuli along the experimental continuum significantly louder as compared to the older controls and the individuals with Parkinson's disease. Conclusions The present discrimination data suggest sensory and auditory memory limitations may contribute to the intensity resolution issues associated with Parkinson's disease. Age-related differences in loudness scaling will be reviewed.

Effects of self-reported hearing difficulty on intensity discrimination judgments

Listeners may report difficulty understanding speech, particularly in background noise, despite having normal audiograms that do not suggest a sensorineural hearing loss. One potential cause of this hearing difficulty is auditory neuropathy (AN), a disruption in the function of the auditory nerve. AN may specifically affect auditory nerve fibers that code intensity differences at higher sound levels, resulting in particular difficulty with speech recognition but preserved audiometric thresholds. This study aims to detect AN by measuring intensity discrimination thresholds at different frequencies and sound levels, comparing performance to self-reported measures of hearing difficulty. Listeners performed an intensity discrimination task where they heard pairs of tones and judged whether the first or second tone was louder. Psychophysical functions were computed to measure listeners' discrimination thresholds and point of subjective equality (PSE, i.e., point at which the two tones are judged to have equal intensity). Results showed that listeners who report greater speech-in-noise difficulty had shifted PSEs specifically at higher sound levels (60–70 dB SPL, the range used in conversational speech), such that they were more likely to perceive the second tone as louder than it was. The results suggest that an intensity discrimination task may be a useful test for AN.

Sucrose intensity coding and decision-making in rat gustatory cortices.

Sucrose's sweet intensity is one attribute contributing to the overconsumption of high-energy palatable foods. However, it is not known how sucrose intensity is encoded and used to make perceptual decisions by neurons in taste-sensitive cortices. We trained rats in a sucrose intensity discrimination task and found that sucrose evoked a widespread response in neurons recorded in posterior-Insula (pIC), anterior-Insula (aIC), and Orbitofrontal cortex (OFC). Remarkably, only a few Intensity-selective neurons conveyed the most information about sucrose's intensity, indicating that for sweetness the gustatory system uses a compact and distributed code. Sucrose intensity was encoded in both firing-rates and spike-timing. The pIC, aIC, and OFC neurons tracked movement direction, with OFC neurons yielding the most robust response. aIC and OFC neurons encoded the subject's choices, whereas all three regions tracked reward omission. Overall, these multimodal areas provide a neural representation of perceived sucrose intensity, and of task-related information underlying perceptual decision-making.

Perceptual manifestations of auditory modulation during speech planning.

Recent studies have provided electrophysiological evidence that the auditory system's response to externally generated auditory stimuli during speech planning is modulated in comparison to its responses to identical stimuli during no-speaking control conditions. In this study, we examined whether such neural modulations during speech planning result in measurable perceptual modulations. In a two-interval forced choice intensity discrimination paradigm, participants were asked to judge the intensity of a standard tone (with constant intensity), played during a fixation period, relative to the intensity of a comparison tone (with varying intensity), played during speech planning or during no-speaking conditions (silent reading and passive listening). Psychometric functions were fitted to participants' responses in each condition; psychometric functions were used to calculate the point of subjective equality (as a measure of perceptual threshold) and the slope of the psychometric functions (as a measure of perceptual uncertainty). We found that the point of subjective equality in the speaking condition was statistically significantly larger than that in the no-speaking conditions. In addition, slope values in the speaking and listening conditions were statistically significantly smaller than slope value in the silent reading condition. Together, these results suggest that previously reported electrophysiological modulations of the auditory system during speech planning may have perceptual manifestations, such as increases in perceptual thresholds and uncertainty of perceptual thresholds in an intensity discrimination task.

Normalization Models of Contextualized Touch

Divisive normalization is a canonical computation that explains contextual modulation of visual perception and neural responses in the visual system. Conceivably, normalization also underlies contextual modulation of bimanual touch, a perceptual process that likely requires combining what is felt on the hands with where the hands are located in space. Here, we evaluated participants’ ability to perform tactile discrimination tasks on one hand while we manipulated the tactile cues experienced on the other hand and the relative positions of the hands. We found that touch experienced on one hand systematically modulates how touch is perceived on the other hand. Notably, bimanual interaction patterns and their sensitivity to hand locations differed depending on whether participants performed a frequency or intensity discrimination task. In rigorous model competition, we found that these feature-dependent bimanual modulation patterns were well explained by distinct cue combination models that each comprised divisive normalization. Our findings indicate that, while feature-specific rules govern bimanual touch, normalization underlies contextual modulation between the hands.

RETRACTED ARTICLE: Neural auditory intensity discrimination during naturalistic listening: a brain decoding study.

Neural discrimination of auditory intensity is one of the fundamental questions in human auditory perception. Human neuroimaging studies have demonstrated specific neural activations during intensity discrimination tasks. The detailed functional anatomy, however, remains elusive. Most of the existing studies examined the entire auditory cortex as a whole, neglecting the potential functional differentiation within the auditory cortex. Moreover, these previous results based on controlled auditory stimuli might not necessarily extend to the neural mechanism of natural auditory processing. In this study, we propose a novel brain decoding method to examine neural encoding of intensity discrimination during naturalistic auditory experience. Here, we used publically available dataset (http://studyforrest.org) in which high resolution functional magnetic resonance imaging (fMRI) was acquired when the participants freely listened to the audio-version of the movie “Forrest Gump”. We found the sensitivity and accuracy of intensity discrimination in the auditory cortex critically depend on the divergences in intensity levels, yielding a sigmoidal relationship. Furthermore, anatomical subdivisions of auditory cortex revealed great functional diversity and lateralization in intensity discrimination. While bilateral activations were observed in primary auditory cortex, enhanced left-lateralization effects were shown in inferior frontal gyrus, anterior middle temporal gyrus and temporal-occipital junction. Our findings underscore the value of naturalistic paradigms in mapping auditory processing in the brain: naturalistic paradigm contains enriched and complex natural sounds, which not only improve the ecological validity but also alleviate the discrepancies caused by the differences in stimulus types and task designs in previous studies. The multidisciplinary methodology we developed here provides an analytical framework for studying neural encoding of complex auditory stimuli.

Using detection theory to analyze human decision making and sensory processing

On the 50th anniversary of the publication of Green and Swets’ book “Signal Detection Theory and Psychophysics,” it is fitting to revisit the question of how detection theory models of human decision making can improve our understanding of sensory processing. Classical psychophysics, as conceived by Fechner in 1850, trusts the observer to report sensory experiences without bias. The innovation of signal detection theory (SDT) was to develop methods that do not require the observer to have introspective awareness of internal sensations. Since its introduction, SDT has inspired experimentalists in many fields, and so now it is appropriate to simply refer to “detection theory” (DT) as the models are appropriate to a wide range of experiments, many of which do not involve signals in noise per se. Data from a previously published intensity discrimination task relying upon working memory (Gallun et al., 2012) will be examined in greater detail to show the techniques and benefits of a detection theory approach t...

In young readers, the left hemisphere supports the link between temporal processing and phonological awareness

Phonological awareness, the ability to manipulate the sounds of language, is key for learning to read. The first step towards phonological competence is identification of syllables and rimes. In a continuous speech stream, syllables and rimes are marked by slow temporal rhythmic modulations, including changes in vowel intensity or amplitude rise time (ART). Prior work suggests that children's sensitivity to ART predicts reading ability and dyslexia across languages. Yet, little is known about the brain bases of this sensitivity that might be key to both language and reading acquisition. The present study explored the hypothesis that children's brain response to slow temporal modulations, tested with amplitude rise perception, relates to child reading acquisition. Fifteen young readers (ages 7–12) completed ART and a control intensity discrimination task during functional magnetic resonance imaging. Behavioral findings validated the link between ART sensitivity, language and literacy abilities in young readers. Neuroimaging findings showed that while bilateral temporal cortexes were active during the ART task, children with better phonological and ART abilities showed reduced brain activation in left temporal lobe. These findings suggest a link between amplitude rise perception and left-lateralized language abilities, and carry implications for better understanding of language, literacy, and reading disability across languages.

The relationship of phonological ability, speech perception, and auditory perception in adults with dyslexia.

This study investigated whether auditory, speech perception, and phonological skills are tightly interrelated or independently contributing to reading. We assessed each of these three skills in 36 adults with a past diagnosis of dyslexia and 54 matched normal reading adults. Phonological skills were tested by the typical threefold tasks, i.e., rapid automatic naming, verbal short-term memory and phonological awareness. Dynamic auditory processing skills were assessed by means of a frequency modulation (FM) and an amplitude rise time (RT); an intensity discrimination task (ID) was included as a non-dynamic control task. Speech perception was assessed by means of sentences and words-in-noise tasks. Group analyses revealed significant group differences in auditory tasks (i.e., RT and ID) and in phonological processing measures, yet no differences were found for speech perception. In addition, performance on RT discrimination correlated with reading but this relation was mediated by phonological processing and not by speech-in-noise. Finally, inspection of the individual scores revealed that the dyslexic readers showed an increased proportion of deviant subjects on the slow-dynamic auditory and phonological tasks, yet each individual dyslexic reader does not display a clear pattern of deficiencies across the processing skills. Although our results support phonological and slow-rate dynamic auditory deficits which relate to literacy, they suggest that at the individual level, problems in reading and writing cannot be explained by the cascading auditory theory. Instead, dyslexic adults seem to vary considerably in the extent to which each of the auditory and phonological factors are expressed and interact with environmental and higher-order cognitive influences.

Why do forward maskers affect auditory intensity discrimination? Evidence from "molecular psychophysics".

Nonsimultaneous maskers can strongly impair performance in an auditory intensity discrimination task. Using methods of molecular psychophysics, we quantified the extent to which (1) a masker-induced impairment of the representation of target intensity (i.e., increase in internal noise) and (2) a systematic influence of the masker intensities on the decision variable contribute to these effects. In a two-interval intensity discrimination procedure, targets were presented in quiet, and combined with forward maskers. The lateralization of the maskers relative to the targets was varied via the interaural time difference. Intensity difference limens (DLs) were strongly elevated under forward masking but less with contralateral than with ipsilateral maskers. For most listeners and conditions, perceptual weights measuring the relation between the target and masker levels and the response in the intensity discrimination task were positive and significant. Higher perceptual weights assigned to the maskers corresponded to stronger elevations of the intensity DL. The maskers caused only a weak increase in internal noise, unrelated to target level and masker lateralization. The results indicate that the effects of forward masking on intensity discrimination are determined by an inclusion of the masker intensities in the decision variable, compatible with the hypothesis that the impairment in performance is to a large part caused by difficulties in directing selective attention to the targets. The effects of masker lateralization are evidence for top-down influences, and the observed positive signs of the masker weights suggest that the relevant mechanisms are located at higher processing stages rather than in the auditory periphery.

Effect of Changes in Stimulus Site on Activation of the Posterior Parietal Cortex

A previous functional magnetic resonance imaging study elucidated the specific activity of the inferior parietal lobe (IPL) during a two-point discrimination task compared with that during an intensity discrimination task Akatsuka et al. (Neuroimage 40: 852-858, 2008). If the posterior parietal cortex (PPC), including IPL, is responsible for detecting changes in stimulus sites, PPC activity depends on the level of change at stimulus sites. The aim of this study was to clarify whether a particular site exists that could detect changes in stimulus sites using the oddball paradigm. Somatosensory-evoked magnetic fields were recorded in 10 right-handed subjects. Three oddball conditions were performed by all subjects, with the probability of deviant and standard stimuli being 20 and 80%, respectively, under all three conditions. Deviant stimuli were always presented to the second digit of the hand and standard stimuli were presented to the first (small deviance: SD) and fifth digits (medium deviance: MD) of the hand and the first digit of the toe (large deviance: LD). Inter-stimulus intervals were set at 500ms. A brain electrical source analysis showed that activities of areas 1 and 3b elicited by the deviant stimuli were not significantly different among the three conditions. In contrast, PPC activity was significantly greater for LD than for SD and MD. PPC activity tended to increase with greater deviance at stimulus sites, but activities of areas 1 and 3b did not differ. These findings suggest that PPC may have a functional role in automatic change detection systems with regard to deviance of stimulus sites.

Correction: Factors Limiting Performance in a Multitone Intensity-Discrimination Task: Disentangling Non-Optimal Decision Weights and Increased Internal Noise

Correction: Factors Limiting Performance in a Multitone Intensity-Discrimination Task: Disentangling Non-Optimal Decision Weights and Increased Internal Noise

Behavioral and neuronal sensitivity concerning objective measures of auditory stream segregation

To evaluate possible mechanisms of auditory stream segregation, it is desirable to directly compare perceptual stream segregation and its neurophysiological correlate. Objective measures of stream segregation, i.e., measures of perceptual sensitivity that differ between conditions in which one integrated stream or two segregated streams are perceived, lend themselves to the study of such phenomena. They can be applied both in studies involving human subjects and in animal studies on auditory streaming. On the one hand, we present results from a study on informational masking in Mongolian gerbils, in which better performance in an intensity discrimination task is observed if streams of target signals and distractors are processed in separate streams. On the other hand, we present results from a temporal pattern discrimination experiment in European starlings, in which better performance is achieved if the target signals and signals useful for temporal reference are processed within one stream rather than i...

Factors Limiting Performance in a Multitone Intensity-Discrimination Task: Disentangling Non-Optimal Decision Weights and Increased Internal Noise

To identify factors limiting performance in multitone intensity discrimination, we presented sequences of five pure tones alternating in level between loud (85 dB SPL) and soft (30, 55, or 80 dB SPL). In the “overall-intensity task”, listeners detected a level increment on all of the five tones. In the “masking task”, the level increment was imposed only on the soft tones, rendering the soft tones targets and loud tones task-irrelevant maskers. Decision weights quantifying the importance of the five tone levels for the decision were estimated using methods of molecular psychophysics. Compatible with previous studies, listeners placed higher weights on the loud tones than on the soft tones in the overall-intensity condition. In the masking task, the decisions were systematically influenced by the to-be-ignored loud tones (maskers). Using a maximum-likelihood technique, we estimated the internal noise variance and tested whether the internal noise was higher in the alternating-level five-tone sequences than in sequences presenting only the soft or only the loud tones. For the overall-intensity task, we found no evidence for increased internal noise, but listeners applied suboptimal decision weights. These results are compatible with the hypothesis that the presence of the loud tones does not impair the precision of the representation of the intensity of the soft tones available at the decision stage, but that this information is not used in an optimal fashion due to a difficulty in attending to the soft tones. For the masking task, in some cases our data indicated an increase in internal noise. Additionally, listeners applied suboptimal decision weights. The maximum-likelihood analyses we developed should also be useful for other tasks or other sensory modalities.

Temporal and non-temporal processes in the elderly

The present study examined whether the reported age-related decline in auditory temporal resolution is specific to the temporal domain or rather reflects a general decline in auditory perception, including the stimulus intensity domain. The performance of 89 healthy participants aged between 21 and 82 years with normal hearing was tested on a variety of psychophysical tasks, where discrimination was based either on the temporal or on the intensity domains. Stimulus levels for all tasks were 40 dB SL (corrected for threshold). Participants were also tested on two cognitive tasks: Wechsler Adult Intelligence Scale, Third Edition, matrices and digit span. Findings indicate that age was significantly negatively correlated with performance on three of the temporal resolution tasks, namely, dichotic temporal-order judgment, spectral temporal-order judgment, and gap detection, but not on the intensity discrimination task, thus emphasizing the specificity of the age-related decline to the auditory temporal domain. The overall results suggest that age-related changes in auditory perception are specific to the temporal domain, even when controlling for hearing sensitivity and cognitive ability, and are not reflected in other aspects of non-temporal perception, such as intensity discrimination.

Binaural release from masking in forward-masked intensity discrimination: Evidence for effects of selective attention

In a forward-masked intensity discrimination task, we manipulated the perceived lateralization of the masker via variation of the interaural time difference (ITD). The maskers and targets were 500 Hz pure tones with a duration of 30 ms. Standards of 30 and 60 dB SPL were combined with 60 or 90 dB SPL maskers. As expected, the presentation of a forward masker perceived as lateralized to the other side of the head as the target resulted in a significantly smaller elevation of the intensity difference limen than a masker lateralized ipsilaterally. This binaural release from masking in forward-masked intensity discrimination cannot be explained by peripheral mechanisms because varying the ITD leaves the neural representation in the monaural channels (i.e., in the auditory nerve) unaltered. Instead, our results are compatible with the assumption that lateralization differences between masker and target promote object segregation and therefore facilitate object-based selective attention to the target.