Christian Lorenzi

Christian Lorenzi (born April 15, 1968) is Professor of Experimental Psychology at École Normale Supérieure in Paris, France, where he has been Director of the Department of Cognitive Studies and Director of Scientific Studies until.[1] Lorenzi works on auditory perception.

Christian Lorenzi
Born (1968-04-15) April 15, 1968
EducationPhD, Université Lyon 2, France, 1995
Scientific career
FieldsAuditory sciences
InstitutionsÉcole Normale Supérieure, Paris, France
Thesis"Codage de la modulation d'amplitude dans le système auditif: expériences psychoacoustiques et modélisation physiologique" (1995)
Websitelsp.dec.ens.fr/en/member/646/christian-lorenzi

Biography

Lorenzi obtained a PhD in experimental psychology from Université Lyon 2 in 1995[2] for his work on "Codage de la modulation d'amplitude dans le système auditif: expériences psychoacoustiques et modélisation physiologique" (coding of amplitude modulation in the auditory system: psychoacoustical experiments and physiological modelling). He then spent a year as a postdoc at the Applied Psychology Unit in Cambridge, UK, where he worked with Roy D. Patterson on the perception of click trains.[3] The following year, he moved to the Glasgow branch of the MRC Institute of Hearing Research where he worked with Stuart Gatehouse.[4]

Back in France, he became Lecturer (Maître de Conférences) at the Université Paris Descartes. He obtained his Habilitation à Diriger les Recherches in 2000 and became Professor in 2001.[5] During this period, he is a member of the Laboratoire de Psychologie de la Perception where he worked on the creation of the Équipe Audition which becomes physically located at the ENS.[6] In 2011, his affiliation officially changed to the École Normale Supérieure, where he was Director of Scientific Studies until 2020.

Lorenzi became a fellow of the Acoustical Society of America in 2008.[7]

Research

Sounds such as speech are decomposed by the peripheral auditory system of humans (the cochlea) into narrow frequency bands. The resulting signals convey information at different time scales to more central auditory structures. A dichotomy between slow "temporal envelope" cues and faster "temporal fine structure" (TFS) cues has been proposed to explore several aspects of auditory perception including speech intelligibility in quiet or against competing sound sources.

Starting from the late nineties, Lorenzi conducted a research program on auditory perception combining signal processing, psychophysical, electrophysiological and computational methods based on this envelope/TFS dichotomy. He examined the role of these two cues in sound discrimination and identification and auditory scene analysis, how these cues are processed at each stage of the auditory system, and the effects of peripheral (cochlear) or central damage, ageing and rehabilitation systems (e.g., hearing aids or cochlear implants) on the perception of these temporal envelope and TFS cues.

His early work on the perception of temporal-envelope information corroborated the existence of tuned (selective) modulation filters at central stages of the human auditory system, consistent with the notion that the auditory system computes some form of modulation spectrum of incoming sounds.[8][9] He then showed that dynamic information in sounds not only is carried by so-called first-order characteristic of sounds (e.g., onset and offset cues, slow amplitude modulations composing the envelope of sounds), but also can be carried by temporal variations in “second-order” characteristics such as the temporal-envelope contrast (depth). His psychophysical conducted on normal-hearing people and patients with cochlear or brain lesions is consistent with the idea that, as in vision, nonlinear mechanisms along the auditory pathway generate an audible distortion component at the 2nd-order AM frequency in the internal modulation spectrum of sounds.[10]

His more recent work on the perception of TFS information suggested that TFS cues convey as much spectro-temporal information as temporal-envelope cues do for complex sounds such as speech.[11] He also showed that TFS cues are less vulnerable than temporal envelope cues when sounds are masked by competing sounds such as noise or presented at high intensities, and may play a role in robust sound coding at the low (brainstem) level.[11][12] His work conducted with people with sensorineural hearing loss and computational models of auditory perception showed how cochlear lesions may alter the neural representation of TFS cues in the early stages of the auditory system, even in regions of the pure-tone audiogram where hearing is clinically considered as normal.[13][14]

See also

References
  1. "Rencontre avec les directeurs d'études de l'École normale – ENS". www.ens.psl.eu. Retrieved 14 July 2020.
  2. "Atelier National de Reproduction des Thèses". Retrieved 10 March 2018.
  3. Tsuzaki, M.; Patterson, R. D.; Lorenzi, C. (1996). "Detecting time and amplitude jitter in a click train". The Journal of the Acoustical Society of America. 100 (4): 2681–2681. doi:10.1121/1.416966.
  4. Lorenzi, C.; Gatehouse, S.; Lever, C. (1997). "Sound localization in noise in hearing‐impaired listeners". The Journal of the Acoustical Society of America. 101 (5): 3104–3105. doi:10.1121/1.418860.
  5. "Collège de France" (PDF). Retrieved 10 March 2018.
  6. "Laboratoire de Psychologie de la Perception". Archived from the original on 2006-06-21. Retrieved 2019-07-01.
  7. "Fellows". Acoustical Society of America. Retrieved 10 March 2018.
  8. Giraud, Anne-Lise; Lorenzi, Christian; Ashburner, John; Wable, Jocelyne; Johnsrude, Ingrid; Frackowiak, Richard; Kleinschmidt, Andreas (September 2000). "Representation of the Temporal Envelope of Sounds in the Human Brain". Journal of Neurophysiology. 84 (3): 1588–1598. doi:10.1152/jn.2000.84.3.1588. PMID 10980029.
  9. Liegeois-Chauvel, C.; Lorenzi, C.; Trébuchon, A.; Régis, J.; Chauvel, P. (28 March 2004). "Temporal Envelope Processing in the Human Left and Right Auditory Cortices". Cerebral Cortex. 14 (7): 731–740. doi:10.1093/cercor/bhh033. PMID 15054052.
  10. Lorenzi, Christian; Soares, Catherine; Vonner, Thomas (August 2001). "Second-order temporal modulation transfer functions". The Journal of the Acoustical Society of America. 110 (2): 1030–1038. doi:10.1121/1.1383295.
  11. Shamma, Shihab; Lorenzi, Christian (May 2013). "On the balance of envelope and temporal fine structure in the encoding of speech in the early auditory system". The Journal of the Acoustical Society of America. 133 (5): 2818–2833. doi:10.1121/1.4795783. PMC 3663870. PMID 23654388.
  12. Paraouty, Nihaad; Stasiak, Arkadiusz; Lorenzi, Christian; Varnet, Léo; Winter, Ian M. (25 April 2018). "Dual Coding of Frequency Modulation in the Ventral Cochlear Nucleus". The Journal of Neuroscience. 38 (17): 4123–4137. doi:10.1523/JNEUROSCI.2107-17.2018. PMC 6596033. PMID 29599389.
  13. Lorenzi, Christian; Debruille, Louis; Garnier, Stéphane; Fleuriot, Pierre; Moore, Brian C. J. (January 2009). "Abnormal processing of temporal fine structure in speech for frequencies where absolute thresholds are normal". The Journal of the Acoustical Society of America. 125 (1): 27–30. doi:10.1121/1.2939125.
  14. Wallaert, Nicolas; Varnet, Léo; Moore, Brian C. J.; Lorenzi, Christian (August 2018). "Sensorineural hearing loss impairs sensitivity but spares temporal integration for detection of frequency modulation". The Journal of the Acoustical Society of America. 144 (2): 720–733. doi:10.1121/1.5049364.
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