Limits...
Alpha oscillations and early stages of visual encoding.

Klimesch W, Fellinger R, Freunberger R - Front Psychol (2011)

Bottom Line: The physiological function of alpha is interpreted in terms of inhibition.We assume that alpha enables access to stored information by inhibiting task-irrelevant neuronal structures and by timing cortical activity in task relevant neuronal structures.We discuss a variety findings showing that evoked alpha and phase locking reflect successful encoding of global stimulus features in an early post-stimulus interval of about 0-150 ms.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiological Psychology, University of Salzburg Salzburg, Austria.

ABSTRACT
For a long time alpha oscillations have been functionally linked to the processing of visual information. Here we propose an new theory about the functional meaning of alpha. The central idea is that synchronized alpha reflects a basic processing mode that controls access to information stored in a complex long-term memory system, which we term knowledge system in order to emphasize that it comprises not only declarative memories but any kind of knowledge comprising also procedural information. Based on this theoretical background, we assume that during early stages of perception, alpha "directs the flow of information" to those neural structures which represent information that is relevant for encoding. The physiological function of alpha is interpreted in terms of inhibition. We assume that alpha enables access to stored information by inhibiting task-irrelevant neuronal structures and by timing cortical activity in task relevant neuronal structures. We discuss a variety findings showing that evoked alpha and phase locking reflect successful encoding of global stimulus features in an early post-stimulus interval of about 0-150 ms.

No MeSH data available.


Related in: MedlinePlus

The event-related alpha power response is task, not stimulus dependent. Alpha power changes were determined relative to a pre-stimulus reference interval and were calculated as percentage or z-values. An increase in power is termed event-related synchronization (ERS), a decrease event-related desynchronization (ERD). All of the results shown here are for the upper alpha band (10–12 Hz) and from posterior recording sites [with the exception of the data shown (D) which were recorded from temporal sites]. (A) In a word recognition task, a brief and transient increase in power can be observed in response to the onset of a correctly recognized word. Then, a large ERD develops, reaching a maximum at around 600 ms post-stimulus. Data are replotted from Klimesch et al. (2000). (B) In a visual oddball task a significant ERD can be observed already around 500 ms pre-stimulus. Data are replotted from Klimesch et al. (1998a). (C) An immediate onset of ERD can be observed in a task, in which light flashes were presented when alpha power exceeded a predetermined (individually determined) threshold. Data are replotted from Woertz et al. (2004). (D) In a memory scanning task, ERS can be observed during the presentation of the memory set (i.e., during encoding) but ERD during the processing of the probe item (i.e., during retrieval). Data are replotted from Klimesch et al. (1999).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3108577&req=5

Figure 1: The event-related alpha power response is task, not stimulus dependent. Alpha power changes were determined relative to a pre-stimulus reference interval and were calculated as percentage or z-values. An increase in power is termed event-related synchronization (ERS), a decrease event-related desynchronization (ERD). All of the results shown here are for the upper alpha band (10–12 Hz) and from posterior recording sites [with the exception of the data shown (D) which were recorded from temporal sites]. (A) In a word recognition task, a brief and transient increase in power can be observed in response to the onset of a correctly recognized word. Then, a large ERD develops, reaching a maximum at around 600 ms post-stimulus. Data are replotted from Klimesch et al. (2000). (B) In a visual oddball task a significant ERD can be observed already around 500 ms pre-stimulus. Data are replotted from Klimesch et al. (1998a). (C) An immediate onset of ERD can be observed in a task, in which light flashes were presented when alpha power exceeded a predetermined (individually determined) threshold. Data are replotted from Woertz et al. (2004). (D) In a memory scanning task, ERS can be observed during the presentation of the memory set (i.e., during encoding) but ERD during the processing of the probe item (i.e., during retrieval). Data are replotted from Klimesch et al. (1999).

Mentions: Example 1: The “typical” ERD in response to a visual stimulus. Figure 1A depicts the time course of upper alpha ERD during word recognition (data are replotted from Klimesch et al., 2000). A set of 96 target words (which were presented in a preceding study session) and 96 distractor words were presented in a random sequence (exposure time: 250 ms). The interstimulus-interval was 4 s. Subjects responded by pressing a “yes” or a “no” response key. Mean response times for hits was 966 ms. Data are analyzed only for correctly remembered words. As Figure 1A shows, after a brief increase in amplitudes (ERS) reflecting the influence of early ERP components, a sharp drop in amplitudes (ERD) can be observed that reaches a maximum at around 600 ms. Considering the time needed for the manual response and the mean response time of about 970 ms, the ERD peak at around 600 ms most likely indicates the end of processing the stimulus. The interpretation of this finding is that an increasing ERD reflects an increase in excitation that is associated with different stages of stimulus processing comprising the retrieval and evaluation of a memory trace.


Alpha oscillations and early stages of visual encoding.

Klimesch W, Fellinger R, Freunberger R - Front Psychol (2011)

The event-related alpha power response is task, not stimulus dependent. Alpha power changes were determined relative to a pre-stimulus reference interval and were calculated as percentage or z-values. An increase in power is termed event-related synchronization (ERS), a decrease event-related desynchronization (ERD). All of the results shown here are for the upper alpha band (10–12 Hz) and from posterior recording sites [with the exception of the data shown (D) which were recorded from temporal sites]. (A) In a word recognition task, a brief and transient increase in power can be observed in response to the onset of a correctly recognized word. Then, a large ERD develops, reaching a maximum at around 600 ms post-stimulus. Data are replotted from Klimesch et al. (2000). (B) In a visual oddball task a significant ERD can be observed already around 500 ms pre-stimulus. Data are replotted from Klimesch et al. (1998a). (C) An immediate onset of ERD can be observed in a task, in which light flashes were presented when alpha power exceeded a predetermined (individually determined) threshold. Data are replotted from Woertz et al. (2004). (D) In a memory scanning task, ERS can be observed during the presentation of the memory set (i.e., during encoding) but ERD during the processing of the probe item (i.e., during retrieval). Data are replotted from Klimesch et al. (1999).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108577&req=5

Figure 1: The event-related alpha power response is task, not stimulus dependent. Alpha power changes were determined relative to a pre-stimulus reference interval and were calculated as percentage or z-values. An increase in power is termed event-related synchronization (ERS), a decrease event-related desynchronization (ERD). All of the results shown here are for the upper alpha band (10–12 Hz) and from posterior recording sites [with the exception of the data shown (D) which were recorded from temporal sites]. (A) In a word recognition task, a brief and transient increase in power can be observed in response to the onset of a correctly recognized word. Then, a large ERD develops, reaching a maximum at around 600 ms post-stimulus. Data are replotted from Klimesch et al. (2000). (B) In a visual oddball task a significant ERD can be observed already around 500 ms pre-stimulus. Data are replotted from Klimesch et al. (1998a). (C) An immediate onset of ERD can be observed in a task, in which light flashes were presented when alpha power exceeded a predetermined (individually determined) threshold. Data are replotted from Woertz et al. (2004). (D) In a memory scanning task, ERS can be observed during the presentation of the memory set (i.e., during encoding) but ERD during the processing of the probe item (i.e., during retrieval). Data are replotted from Klimesch et al. (1999).
Mentions: Example 1: The “typical” ERD in response to a visual stimulus. Figure 1A depicts the time course of upper alpha ERD during word recognition (data are replotted from Klimesch et al., 2000). A set of 96 target words (which were presented in a preceding study session) and 96 distractor words were presented in a random sequence (exposure time: 250 ms). The interstimulus-interval was 4 s. Subjects responded by pressing a “yes” or a “no” response key. Mean response times for hits was 966 ms. Data are analyzed only for correctly remembered words. As Figure 1A shows, after a brief increase in amplitudes (ERS) reflecting the influence of early ERP components, a sharp drop in amplitudes (ERD) can be observed that reaches a maximum at around 600 ms. Considering the time needed for the manual response and the mean response time of about 970 ms, the ERD peak at around 600 ms most likely indicates the end of processing the stimulus. The interpretation of this finding is that an increasing ERD reflects an increase in excitation that is associated with different stages of stimulus processing comprising the retrieval and evaluation of a memory trace.

Bottom Line: The physiological function of alpha is interpreted in terms of inhibition.We assume that alpha enables access to stored information by inhibiting task-irrelevant neuronal structures and by timing cortical activity in task relevant neuronal structures.We discuss a variety findings showing that evoked alpha and phase locking reflect successful encoding of global stimulus features in an early post-stimulus interval of about 0-150 ms.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiological Psychology, University of Salzburg Salzburg, Austria.

ABSTRACT
For a long time alpha oscillations have been functionally linked to the processing of visual information. Here we propose an new theory about the functional meaning of alpha. The central idea is that synchronized alpha reflects a basic processing mode that controls access to information stored in a complex long-term memory system, which we term knowledge system in order to emphasize that it comprises not only declarative memories but any kind of knowledge comprising also procedural information. Based on this theoretical background, we assume that during early stages of perception, alpha "directs the flow of information" to those neural structures which represent information that is relevant for encoding. The physiological function of alpha is interpreted in terms of inhibition. We assume that alpha enables access to stored information by inhibiting task-irrelevant neuronal structures and by timing cortical activity in task relevant neuronal structures. We discuss a variety findings showing that evoked alpha and phase locking reflect successful encoding of global stimulus features in an early post-stimulus interval of about 0-150 ms.

No MeSH data available.


Related in: MedlinePlus