Temporal information in the range of tens to
hundreds of ms is fundamental to many forms of sensory processing.
Motion processing is a ubiquitous example in the auditory,
somatosensory, and visual domains of a task that requires temporal
information. However, it is arguably in the auditory
domain that timing is most prominent, owing to
its importance in vocalization and speech recognition.
The temporal structure within each syllable and
phoneme also contributes to speech recognition. Specifically,
temporal features are fundamental for phoneme
discrimination. These features include voice- onset time (the
time between air release and vocal cord vibration), which
contributes to the “ba” × “pa”
discrimination (Lisker & Abramson 1964), the duration of
frequency transitions (e.g., “ba” ×
“wa”; Liberman et al. 1956), and the silent time
between consonants and vowels (e.g., “sa” ×
“sta”; Dorman et al. 1979). Additionally, prosodic cues
such as pauses and duration of speech segments are used to
determine semantic content (Lehiste et al. 1976).
Owing to the multiple levels and scales of
temporal information in addition to spatial information, speech
is one of the most complex forms of pattern recognition and
requires both spatial and temporal processing (Shannon et al.
1995,Tallal 1994, Doupe & Kuhl 1999). Various lines of evidence
have revealed the degree to which speech recognition relies on
temporal information. Indeed, in some cases it canrely primarily on
the temporal structure.
Given the importance of temporal information in
speech and language it would be expected that deficits in
temporal processing would produce language deficits. Indeed,
it has been suggested that certain forms of language-based learning
disabilities may be caused by generalized sensory deficits
in temporal processing (Livingstone et al. 1991, Eden et al.
1996, Tallal & Piercy 1973; for a review seeFarmer & Klein