Recent Publications de Boer J, Thornton AR, Krumbholz K (2012) What is the role of the medial olivocochlear system in speech-in-noise processing? Journal of Neurophysiology, in press [PubMed] [DOI] Sereda M, Hall DA, Bosnyak DJ, Edmondson-Jones M, Roberts LE, Adjamian P, Palmer AR (2011) Re-examining the relationship between audiometric profile and tinnitus pitch. International Journal of Audiology 50(5), 303-12 [Open Access Article (UKPMC)] [PubMed] Lutkenhoner B, Seither-Preisler A, Krumbholz K, Patterson RD (2011) Auditory cortex tracks the temporal regularity of sustained noisy sounds. Hearing Research 272(1-2), 85-94 [PubMed] [DOI] Magezi DA, Krumbholz K (2010) Evidence for opponent-channel coding of interaural time differences in human auditory cortex. Journal of Neurophysiology 104(4), 1997-2007 [Open Access Article] [PubMed] Edmonds BA, James RE, Utev A, Vestergaard MD, Patterson RD, Krumbholz K (2010) Evidence for early specialized processing of speech formant information in anterior and posterior human auditory cortex. European Journal of Neuroscience 32(4), 684-92 [PubMed] [DOI] Paltoglou AE, Sumner CJ, Hall DA (2009) Examining the role of frequency specificity in the enhancement and suppression of human cortical activity by auditory selective attention. Hearing Rresearch 257(1-2), 106-18 [PubMed] [DOI] Adjamian P, Sereda M, Hall DA (2009) The mechanisms of tinnitus: perspectives from human functional neuroimaging. Hearing Research 253(1-2), 15-31 [PubMed] [DOI] View all publications from this research group
When we perceive sounds, the brain is constantly converting the incoming acoustical information into neural representations. For this conversion, the brain has to first extract the information relating to the different features of the sound (e.g., pitch, sound location or vowel type), and then represent this information in a way that makes it accessible to higher-level processes like attention. We use both perceptual, or “psychoacoustic”, experiments and non-invasive brain imaging methods to investigate the mechanisms of these different processing stages.
In our previous psychoacoustic work, we explored how the brain processes the millisecond and sub-millisecond temporal information that the auditory nerve conveys. This fine-grain temporal information is thought to play a crucial role for the perception of pitch in music and speech and for sound localisation.
Figure 1: Psychoacoustic data (left) and model simulations (right) investigating pitch perception mechanisms
We use functional magnetic resonance imaging (fMRI) to investigate how information about these features is represented at higher stages in the brain. FMRI measures neural activity indirectly and enables to visualise brain activation with a high spatial resolution. Our work is aimed at developing methods to exploit the spatial precision of fMRI for revealing functional organisation in auditory cortex at the columnar scale.
Figure 2: Voxel tuning curves for sound frequency (left), pitch (middle) and sound azimuth (right) measured with high-resolution fMRI
Electroencephalography (EEG) is another method to measure brain responses. Unlike fMRI, EEG provides a direct measure of neural activity. While EEG has a comparatively poor spatial resolution, it has excellent temporal acuity and is thus complementary to fMRI. We use EEG to investigate how the brain response to sound is affected by prior stimulation.
Figure 3: Brain response to sound measured through EEG (top). The scalp distribution of the response is used to make conclusions about the location of the source (bottom)