Limits...
Differential activation of human core, non-core and auditory-related cortex during speech categorization tasks as revealed by intracranial recordings.

Steinschneider M, Nourski KV, Rhone AE, Kawasaki H, Oya H, Howard MA - Front Neurosci (2014)

Bottom Line: While non-primary auditory cortex located on the posterolateral superior temporal gyrus (PLST) is clearly involved in acoustic-to-phonetic pre-lexical representations, it is unclear what role this region plays in auditory object formation.We found that activity in posteromedial HG and early activity on PLST was robust to sound stimuli regardless of their context, and minimally modulated by tasks.Activity in prefrontal cortex appears directly involved in word object selection.

View Article: PubMed Central - PubMed

Affiliation: Departments of Neurology and Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA.

ABSTRACT
Speech perception requires that sounds be transformed into speech-related objects with lexical and semantic meaning. It is unclear at what level in the auditory pathways this transformation emerges. Primary auditory cortex has been implicated in both representation of acoustic sound attributes and sound objects. While non-primary auditory cortex located on the posterolateral superior temporal gyrus (PLST) is clearly involved in acoustic-to-phonetic pre-lexical representations, it is unclear what role this region plays in auditory object formation. Additional data support the importance of prefrontal cortex in the formation of auditory objects, while other data would implicate this region in auditory object selection. To help clarify the respective roles of auditory and auditory-related cortex in the formation and selection of auditory objects, we examined high gamma activity simultaneously recorded directly from Heschl's gyrus (HG), PLST and prefrontal cortex, while subjects performed auditory semantic detection tasks. Subjects were patients undergoing evaluation for treatment of medically intractable epilepsy. We found that activity in posteromedial HG and early activity on PLST was robust to sound stimuli regardless of their context, and minimally modulated by tasks. Later activity on PLST could be strongly modulated by semantic context, but not by behavioral performance. Activity within prefrontal cortex also was related to semantic context, and did co-vary with behavior. We propose that activity in posteromedial HG and early activity on PLST primarily reflect the representation of spectrotemporal sound attributes. Later activity on PLST represents a pre-lexical processing stage and is an intermediate step in the formation of word objects. Activity in prefrontal cortex appears directly involved in word object selection. The roles of other auditory and auditory-related cortical areas in the formation of word objects remain to be explored.

No MeSH data available.


Related in: MedlinePlus

Task effects on responses to speech stimuli (female voices) in PLST. (A) MRI of the left hemisphere in subject L275 showing the locations of chronically implanted subdural grid contacts. (B) High gamma responses to syllables spoken by females, presented in three different tasks (different colors), are shown for the 96-contact recording grid implanted over perisylvian cortex. Gray lines represent approximate boundaries of STG, IFG, pre- and post-central gyri covered by the recording grid. (C) High gamma ERBP time course replotted for three recording sites on PLST. Lines and shaded areas represent mean high gamma ERBP and its standard error, respectively. Purple bars denote time windows where responses to the target stimuli were significantly larger than those to the same stimuli in the tones task (q < 0.01). Horizontal box plot denotes the timing of behavioral responses to the target stimulus (median, 10th, 25th, 75th, and 90th percentiles).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4128221&req=5

Figure 3: Task effects on responses to speech stimuli (female voices) in PLST. (A) MRI of the left hemisphere in subject L275 showing the locations of chronically implanted subdural grid contacts. (B) High gamma responses to syllables spoken by females, presented in three different tasks (different colors), are shown for the 96-contact recording grid implanted over perisylvian cortex. Gray lines represent approximate boundaries of STG, IFG, pre- and post-central gyri covered by the recording grid. (C) High gamma ERBP time course replotted for three recording sites on PLST. Lines and shaded areas represent mean high gamma ERBP and its standard error, respectively. Purple bars denote time windows where responses to the target stimuli were significantly larger than those to the same stimuli in the tones task (q < 0.01). Horizontal box plot denotes the timing of behavioral responses to the target stimulus (median, 10th, 25th, 75th, and 90th percentiles).

Mentions: More complex response profiles were observed on PLST (Figures 3, 4) when compared with profiles simultaneously recorded from HG (see Figure 2). There was a rapid and large increase in high gamma ERBP occurring within 200 ms after stimulus onset. This early activity was variably affected by the task [e.g. sites (a), (b), and (c) in Figures 3, 4]. When female voices were targets, a modest but significant increase in high gamma power was observed as early as 50–100 ms after stimulus onset. Peak activity at 150–200 ms was only marginally affected by the task. Later activity was more variable across recording sites. Both enhancement of high gamma activity to the target syllables beginning prior to their offsets [e.g. sites (a), (b), and (c) in Figure 3] and minimal modulation of later activity related to the task (see Figure 3B) were observed in this region. Task-related high gamma activity was earlier than that occurring in HG (cf. Figure 2) and preceded the subject's behavioral response.


Differential activation of human core, non-core and auditory-related cortex during speech categorization tasks as revealed by intracranial recordings.

Steinschneider M, Nourski KV, Rhone AE, Kawasaki H, Oya H, Howard MA - Front Neurosci (2014)

Task effects on responses to speech stimuli (female voices) in PLST. (A) MRI of the left hemisphere in subject L275 showing the locations of chronically implanted subdural grid contacts. (B) High gamma responses to syllables spoken by females, presented in three different tasks (different colors), are shown for the 96-contact recording grid implanted over perisylvian cortex. Gray lines represent approximate boundaries of STG, IFG, pre- and post-central gyri covered by the recording grid. (C) High gamma ERBP time course replotted for three recording sites on PLST. Lines and shaded areas represent mean high gamma ERBP and its standard error, respectively. Purple bars denote time windows where responses to the target stimuli were significantly larger than those to the same stimuli in the tones task (q < 0.01). Horizontal box plot denotes the timing of behavioral responses to the target stimulus (median, 10th, 25th, 75th, and 90th percentiles).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128221&req=5

Figure 3: Task effects on responses to speech stimuli (female voices) in PLST. (A) MRI of the left hemisphere in subject L275 showing the locations of chronically implanted subdural grid contacts. (B) High gamma responses to syllables spoken by females, presented in three different tasks (different colors), are shown for the 96-contact recording grid implanted over perisylvian cortex. Gray lines represent approximate boundaries of STG, IFG, pre- and post-central gyri covered by the recording grid. (C) High gamma ERBP time course replotted for three recording sites on PLST. Lines and shaded areas represent mean high gamma ERBP and its standard error, respectively. Purple bars denote time windows where responses to the target stimuli were significantly larger than those to the same stimuli in the tones task (q < 0.01). Horizontal box plot denotes the timing of behavioral responses to the target stimulus (median, 10th, 25th, 75th, and 90th percentiles).
Mentions: More complex response profiles were observed on PLST (Figures 3, 4) when compared with profiles simultaneously recorded from HG (see Figure 2). There was a rapid and large increase in high gamma ERBP occurring within 200 ms after stimulus onset. This early activity was variably affected by the task [e.g. sites (a), (b), and (c) in Figures 3, 4]. When female voices were targets, a modest but significant increase in high gamma power was observed as early as 50–100 ms after stimulus onset. Peak activity at 150–200 ms was only marginally affected by the task. Later activity was more variable across recording sites. Both enhancement of high gamma activity to the target syllables beginning prior to their offsets [e.g. sites (a), (b), and (c) in Figure 3] and minimal modulation of later activity related to the task (see Figure 3B) were observed in this region. Task-related high gamma activity was earlier than that occurring in HG (cf. Figure 2) and preceded the subject's behavioral response.

Bottom Line: While non-primary auditory cortex located on the posterolateral superior temporal gyrus (PLST) is clearly involved in acoustic-to-phonetic pre-lexical representations, it is unclear what role this region plays in auditory object formation.We found that activity in posteromedial HG and early activity on PLST was robust to sound stimuli regardless of their context, and minimally modulated by tasks.Activity in prefrontal cortex appears directly involved in word object selection.

View Article: PubMed Central - PubMed

Affiliation: Departments of Neurology and Neuroscience, Albert Einstein College of Medicine Bronx, NY, USA.

ABSTRACT
Speech perception requires that sounds be transformed into speech-related objects with lexical and semantic meaning. It is unclear at what level in the auditory pathways this transformation emerges. Primary auditory cortex has been implicated in both representation of acoustic sound attributes and sound objects. While non-primary auditory cortex located on the posterolateral superior temporal gyrus (PLST) is clearly involved in acoustic-to-phonetic pre-lexical representations, it is unclear what role this region plays in auditory object formation. Additional data support the importance of prefrontal cortex in the formation of auditory objects, while other data would implicate this region in auditory object selection. To help clarify the respective roles of auditory and auditory-related cortex in the formation and selection of auditory objects, we examined high gamma activity simultaneously recorded directly from Heschl's gyrus (HG), PLST and prefrontal cortex, while subjects performed auditory semantic detection tasks. Subjects were patients undergoing evaluation for treatment of medically intractable epilepsy. We found that activity in posteromedial HG and early activity on PLST was robust to sound stimuli regardless of their context, and minimally modulated by tasks. Later activity on PLST could be strongly modulated by semantic context, but not by behavioral performance. Activity within prefrontal cortex also was related to semantic context, and did co-vary with behavior. We propose that activity in posteromedial HG and early activity on PLST primarily reflect the representation of spectrotemporal sound attributes. Later activity on PLST represents a pre-lexical processing stage and is an intermediate step in the formation of word objects. Activity in prefrontal cortex appears directly involved in word object selection. The roles of other auditory and auditory-related cortical areas in the formation of word objects remain to be explored.

No MeSH data available.


Related in: MedlinePlus