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Cortical modulation of auditory processing in the midbrain.

Bajo VM, King AJ - Front Neural Circuits (2013)

Bottom Line: Focal electrical stimulation and inactivation studies have shown that the auditory cortex can modify almost every aspect of the response properties of IC neurons, including their sensitivity to sound frequency, intensity, and location.Along with other descending pathways in the auditory system, the corticocollicular projection appears to continually modulate the processing of acoustical signals at subcortical levels.In particular, there is growing evidence that these circuits play a critical role in the plasticity of neural processing that underlies the effects of learning and experience on auditory perception by enabling changes in cortical response properties to spread to subcortical nuclei.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK.

ABSTRACT
In addition to their ascending pathways that originate at the receptor cells, all sensory systems are characterized by extensive descending projections. Although the size of these connections often outweighs those that carry information in the ascending auditory pathway, we still have a relatively poor understanding of the role they play in sensory processing. In the auditory system one of the main corticofugal projections links layer V pyramidal neurons with the inferior colliculus (IC) in the midbrain. All auditory cortical fields contribute to this projection, with the primary areas providing the largest outputs to the IC. In addition to medium and large pyramidal cells in layer V, a variety of cell types in layer VI make a small contribution to the ipsilateral corticocollicular projection. Cortical neurons innervate the three IC subdivisions bilaterally, although the contralateral projection is relatively small. The dorsal and lateral cortices of the IC are the principal targets of corticocollicular axons, but input to the central nucleus has also been described in some studies and is distinctive in its laminar topographic organization. Focal electrical stimulation and inactivation studies have shown that the auditory cortex can modify almost every aspect of the response properties of IC neurons, including their sensitivity to sound frequency, intensity, and location. Along with other descending pathways in the auditory system, the corticocollicular projection appears to continually modulate the processing of acoustical signals at subcortical levels. In particular, there is growing evidence that these circuits play a critical role in the plasticity of neural processing that underlies the effects of learning and experience on auditory perception by enabling changes in cortical response properties to spread to subcortical nuclei.

No MeSH data available.


Related in: MedlinePlus

Antidromic activation reveals tonotopically organized projections from A1 to the CNIC in guinea pig. Multi-site probes were positioned along the tonotopic axis of the guinea pig CNIC (A) and A1 (B). (C) Post-stimulus time histograms (PSTHs) for eight A1 locations with different best frequencies (BF) from low (location 1) to high (location 8). These responses were evoked by antidromic stimulation equivalent to 10 dB above threshold at eight frequency-matched locations in the IC. Color scale corresponds to the total number of spikes across 40 trials where any values ≤5 and ≥20 were set to white and black, respectively. Modified with permission from Lim and Anderson (2007).
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Figure 6: Antidromic activation reveals tonotopically organized projections from A1 to the CNIC in guinea pig. Multi-site probes were positioned along the tonotopic axis of the guinea pig CNIC (A) and A1 (B). (C) Post-stimulus time histograms (PSTHs) for eight A1 locations with different best frequencies (BF) from low (location 1) to high (location 8). These responses were evoked by antidromic stimulation equivalent to 10 dB above threshold at eight frequency-matched locations in the IC. Color scale corresponds to the total number of spikes across 40 trials where any values ≤5 and ≥20 were set to white and black, respectively. Modified with permission from Lim and Anderson (2007).

Mentions: Anterograde tracing studies have shown that the location of the terminal fields in the CNIC varies topographically with the location of the injection sites in A1 (Saldaña et al., 1996; Bajo et al., 2007). For example, Bajo et al. (2007) found that injecting tracers at two distinct locations in ferret A1, where neurons were tuned to different frequencies, produced two distinct bands of labeling in the CNIC, suggesting that the A1-CNIC projection links neurons in both structures with similar frequency tuning. This has been confirmed physiologically in the guinea pig by positioning multi-site probes along the tonotopic axes of A1 and the CNIC (Lim and Anderson, 2007). After electrically stimulating different locations in the CNIC, these authors recorded antidromic-evoked activity in A1 locations with matching best frequencies (Figure 6). By linking neurons with common sound frequency preferences, this topographic projection provides an anatomical substrate for corticofugal modulation of IC neurons with related receptive field properties.


Cortical modulation of auditory processing in the midbrain.

Bajo VM, King AJ - Front Neural Circuits (2013)

Antidromic activation reveals tonotopically organized projections from A1 to the CNIC in guinea pig. Multi-site probes were positioned along the tonotopic axis of the guinea pig CNIC (A) and A1 (B). (C) Post-stimulus time histograms (PSTHs) for eight A1 locations with different best frequencies (BF) from low (location 1) to high (location 8). These responses were evoked by antidromic stimulation equivalent to 10 dB above threshold at eight frequency-matched locations in the IC. Color scale corresponds to the total number of spikes across 40 trials where any values ≤5 and ≥20 were set to white and black, respectively. Modified with permission from Lim and Anderson (2007).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539853&req=5

Figure 6: Antidromic activation reveals tonotopically organized projections from A1 to the CNIC in guinea pig. Multi-site probes were positioned along the tonotopic axis of the guinea pig CNIC (A) and A1 (B). (C) Post-stimulus time histograms (PSTHs) for eight A1 locations with different best frequencies (BF) from low (location 1) to high (location 8). These responses were evoked by antidromic stimulation equivalent to 10 dB above threshold at eight frequency-matched locations in the IC. Color scale corresponds to the total number of spikes across 40 trials where any values ≤5 and ≥20 were set to white and black, respectively. Modified with permission from Lim and Anderson (2007).
Mentions: Anterograde tracing studies have shown that the location of the terminal fields in the CNIC varies topographically with the location of the injection sites in A1 (Saldaña et al., 1996; Bajo et al., 2007). For example, Bajo et al. (2007) found that injecting tracers at two distinct locations in ferret A1, where neurons were tuned to different frequencies, produced two distinct bands of labeling in the CNIC, suggesting that the A1-CNIC projection links neurons in both structures with similar frequency tuning. This has been confirmed physiologically in the guinea pig by positioning multi-site probes along the tonotopic axes of A1 and the CNIC (Lim and Anderson, 2007). After electrically stimulating different locations in the CNIC, these authors recorded antidromic-evoked activity in A1 locations with matching best frequencies (Figure 6). By linking neurons with common sound frequency preferences, this topographic projection provides an anatomical substrate for corticofugal modulation of IC neurons with related receptive field properties.

Bottom Line: Focal electrical stimulation and inactivation studies have shown that the auditory cortex can modify almost every aspect of the response properties of IC neurons, including their sensitivity to sound frequency, intensity, and location.Along with other descending pathways in the auditory system, the corticocollicular projection appears to continually modulate the processing of acoustical signals at subcortical levels.In particular, there is growing evidence that these circuits play a critical role in the plasticity of neural processing that underlies the effects of learning and experience on auditory perception by enabling changes in cortical response properties to spread to subcortical nuclei.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Anatomy and Genetics, University of Oxford Oxford, UK.

ABSTRACT
In addition to their ascending pathways that originate at the receptor cells, all sensory systems are characterized by extensive descending projections. Although the size of these connections often outweighs those that carry information in the ascending auditory pathway, we still have a relatively poor understanding of the role they play in sensory processing. In the auditory system one of the main corticofugal projections links layer V pyramidal neurons with the inferior colliculus (IC) in the midbrain. All auditory cortical fields contribute to this projection, with the primary areas providing the largest outputs to the IC. In addition to medium and large pyramidal cells in layer V, a variety of cell types in layer VI make a small contribution to the ipsilateral corticocollicular projection. Cortical neurons innervate the three IC subdivisions bilaterally, although the contralateral projection is relatively small. The dorsal and lateral cortices of the IC are the principal targets of corticocollicular axons, but input to the central nucleus has also been described in some studies and is distinctive in its laminar topographic organization. Focal electrical stimulation and inactivation studies have shown that the auditory cortex can modify almost every aspect of the response properties of IC neurons, including their sensitivity to sound frequency, intensity, and location. Along with other descending pathways in the auditory system, the corticocollicular projection appears to continually modulate the processing of acoustical signals at subcortical levels. In particular, there is growing evidence that these circuits play a critical role in the plasticity of neural processing that underlies the effects of learning and experience on auditory perception by enabling changes in cortical response properties to spread to subcortical nuclei.

No MeSH data available.


Related in: MedlinePlus