36x60 poster template

1
Complex Sound Discrimination Abilities in Rats
and the Effects of Multiple Training
Manipulations A.C. Puckett, C.T. Novitski, N.D.
Engineer, A.L. McMenamy, M.S. Perry, C.A. Perez,
P. Kan, Y.H. Chen, V. Jakkamsetti, C.L. Heydrick,
M.P. Kilgard, The University of Texas at Dallas,
Richardson, TX
SPEECH DISCRIMINATION
SEQUENCE DISCRIMINATION
Introduction The current experiments have
examined the ability of rats to perform
discriminations among complex sounds, including
tone-noise sequences and speech stimuli.
Understanding how normal animals are able to
discriminate complex sounds is necessary in order
to fully understand the auditory cortex and how
injury, learning or plasticity can change
perception and cortical functioning.

• Speech Stimulus Creation
• Recording Monosyllabic words spoken by female
  native English speaker in a sound-proof chamber.
• The words dad and tad were recorded from 5
  other native English speakers (3 male, 2 female)
  to assess speaker generalization.
• Frequency shifting The frequency of the
  fundamental and all other formants were shifted
  into the rats hearing range by doubling their
  frequency.
• Compressed versions of dad and tad were
  generated to assess temporal generalization.
• Noise reduction Background noise was subtracted
  from each signal.
• Filtering Each signal was filtered to correct
  for the frequency-response curve of the booth
  speaker.
• Intensity adjustment The RMS-values of the
  signals were adjusted so that the loudest 100 ms
  of each vowel was 60 dB SPL.

n.s.

• Behavioral data was collected from 46 rats over
  4661 total daily training sessions.
• Methods
• All animals performed Go/ No-Go discrimination
  tasks in the same operant training booths. The
  stimuli used as CS and CS- varied among
  different training tasks, but the general
  timeline of training and procedures were the same
  for all tasks.

Dad Tad
HLN NLH
Rad Lad

• Conclusions
• Large spectral differences are easy for rats to
  discriminate, even if differences are not in the
  onset of the speech sound.
• Onsets/consonants /dad/ vs. /bad/ /gad/
• Middle of stimulus/vowels /dad/ vs. /deed/
  /dood/
• Subtle spectral differences are difficult for
  rats to discriminate (and are difficult for
  humans as well).
• Onsets/consonants /rad/ vs. /lad/
• Middle of stimulus/vowels /dad/ vs. /dead/
  /dud/
• Rats can generalize among several variants of a
  speech stimulus.
• Rats could generalize across several compressed
  exemplars, indicating that VOT wasnt the only
  cue.
• Rats could generalize across several different
  speakers. Rats were able to generalize across
  many different fundamental frequencies, temporal
  patterns of enunciation, and other
  idiosyncrasies.
• Speech sounds seem to be more easily
  discriminated than tone-noise sequences.

• Conclusions
• Frequency discriminations are easy, but other
  sequence discriminations are difficult.
• Onsets are the most salient elements of
  sequences.
• Sequences beginning with the same element are
  difficult to discriminate.
• Reversed sequence discrimination was
  impossible, despite different initial elements.
• Sequences may be normally processed as a unit
  rather than discrete elements.
• Discrimination strategies may be changed by
  training.
• If rats learn a poor strategy early in
  training, they will not learn to discriminate
  effectively.
• Intermediate exemplars allowed animals to adopt
  effective strategies.

• Future Directions www.utd.edu/kilgard
• Assessment of changes in perceptual abilities
  after NB-stimulation pairing Amanda Puckett
• Measurement of changes in auditory cortex after
  long-term sequence training Dr. Navzer
  Engineer
• Measurement of responses of auditory cortex
  after long-term speech training Crystal
  Novitski
• Assessment of cortical processing of speech
  sounds after environmental enrichment Vikram
  Jakkamsetti
• Assessment of loss of perceptual abilities
  after cortical injury Dr. Owen Floody
• Information theory analysis of cortical
  responses to speech sounds Helen Chen