Limits...
Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex.

Briley PM, Goman AM, Summerfield AQ - J. Assoc. Res. Otolaryngol. (2016)

Bottom Line: In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location.Adapters came from 0 ° or alternated between left and right (-30 ° and +30 ° or -90 ° and +90 °).The results were consistent with the three-channel account.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of York, York, YO10 5DD, UK. brileypm@gmail.com.

ABSTRACT
Studies with humans and other mammals have provided support for a two-channel representation of horizontal ("azimuthal") space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (-30 ° and +30 ° or -90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance.

No MeSH data available.


Probe responses, shown as source waveforms averaged across participants and cortices, for each combination of probe location (panels) and adapter locations (lines).
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4940291&req=5

Fig1: Probe responses, shown as source waveforms averaged across participants and cortices, for each combination of probe location (panels) and adapter locations (lines).

Mentions: Probe stimuli elicited transient neural responses with peaks corresponding to the P1, N1 and P2 components of the auditory event-related potential (Fig. 1, responses shown collapsed across cortices; Key et al. 2005). The probe response for each condition was quantified as the peak-to-peak amplitude from the N1 to the P2, in line with our previous work (see “METHODS” section). The symbols in Figure 2A plot probe response as a function of adapter azimuth, for each of the three probe locations, collapsed across cortices. As predicted by both the two- and three-channel accounts, the response to the +90 ° probe (triangles) was smallest (i.e. adaptation was greatest) when the adapters were at ±90 °. The probe response was greatest (i.e. adaptation was least) when the adapters were at 0 °.FIG. 1


Physiological Evidence for a Midline Spatial Channel in Human Auditory Cortex.

Briley PM, Goman AM, Summerfield AQ - J. Assoc. Res. Otolaryngol. (2016)

Probe responses, shown as source waveforms averaged across participants and cortices, for each combination of probe location (panels) and adapter locations (lines).
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4940291&req=5

Fig1: Probe responses, shown as source waveforms averaged across participants and cortices, for each combination of probe location (panels) and adapter locations (lines).
Mentions: Probe stimuli elicited transient neural responses with peaks corresponding to the P1, N1 and P2 components of the auditory event-related potential (Fig. 1, responses shown collapsed across cortices; Key et al. 2005). The probe response for each condition was quantified as the peak-to-peak amplitude from the N1 to the P2, in line with our previous work (see “METHODS” section). The symbols in Figure 2A plot probe response as a function of adapter azimuth, for each of the three probe locations, collapsed across cortices. As predicted by both the two- and three-channel accounts, the response to the +90 ° probe (triangles) was smallest (i.e. adaptation was greatest) when the adapters were at ±90 °. The probe response was greatest (i.e. adaptation was least) when the adapters were at 0 °.FIG. 1

Bottom Line: In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location.Adapters came from 0 ° or alternated between left and right (-30 ° and +30 ° or -90 ° and +90 °).The results were consistent with the three-channel account.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, University of York, York, YO10 5DD, UK. brileypm@gmail.com.

ABSTRACT
Studies with humans and other mammals have provided support for a two-channel representation of horizontal ("azimuthal") space in the auditory system. In this representation, location-sensitive neurons contribute activity to one of two broadly tuned channels whose responses are compared to derive an estimate of sound-source location. One channel is maximally responsive to sounds towards the left and the other to sounds towards the right. However, recent psychophysical studies of humans, and physiological studies of other mammals, point to the presence of an additional channel, maximally responsive to the midline. In this study, we used electroencephalography to seek physiological evidence for such a midline channel in humans. We measured neural responses to probe stimuli presented from straight ahead (0 °) or towards the right (+30 ° or +90 °). Probes were preceded by adapter stimuli to temporarily suppress channel activity. Adapters came from 0 ° or alternated between left and right (-30 ° and +30 ° or -90 ° and +90 °). For the +90 ° probe, to which the right-tuned channel would respond most strongly, both accounts predict greatest adaptation when the adapters are at ±90 °. For the 0 ° probe, the two-channel account predicts greatest adaptation from the ±90 ° adapters, while the three-channel account predicts greatest adaptation when the adapters are at 0 ° because these adapters stimulate the midline-tuned channel which responds most strongly to the 0 ° probe. The results were consistent with the three-channel account. In addition, a computational implementation of the three-channel account fitted the probe response sizes well, explaining 93 % of the variance about the mean, whereas a two-channel implementation produced a poor fit and explained only 61 % of the variance.

No MeSH data available.