Cross Modal Sensory Processing Assessments in Rodents

1
Cross Modal Sensory Processing Assessments in
Rodents C. A Cleaver C.A. Hill E. Zhang R.H.
Fitch E.J Markus. Psych. Dept., Behav.
Neurosci. Div., Univ of Conn., Storrs, CT 06269
919.3
INTRODUCTION
RESULTS
VISUAL TASKS
AUDITORY TASKS

• Impairments in speech production and reception
  have been linked to prenatal insult, such as very
  low birth weight (VLBW) and premature births1,2.
  The key impairment seen is reduced rapid auditory
  processing, which has been reported in dyslexic
  and speech impaired subjects who often suffered
  parental insults. Similar deficits have also been
  reported for rapid visual processing for the same
  subject pool. Thus the biological substrate for
  these impairments may be a disruption in neuronal
  development that leads to overarching impairments
  in processing of sensory stimuli. The modal
  chosen to investigate these conditions was
  hypoxic-ischemic insults resulting in
  malformations in the cortex in the rat3,4. The
  histology on the hypoxic-ischemic insults is
  pending, therefore the poster focuses on the sham
  animals. These data will serve as a basis for
  comparison with the brain damaged rats.
• Rats were screened on two auditory and two visual
  tasks.
• How do optimal timing parameters and performance
  compare across modalities?
• Is the performance within a task reliable for an
  individual animal?
• Is performance between two tasks within a given
  modality correlated?
• To what degree is performance between two tasks
  of different modalities correlated?

FM Sweep (Oddball) N16 A linear frequency
downward sweep (2300Hz to 1900Hz, _at_75dB) with a
variable inter-stimulus interval (ISI) between
25-225ms. On cued trials, the direction of the
sweep was reversed. The sweep was presented 50ms
before the SES.
Visual Odd Ball N6 A 4x4 black and white
checkered board pattern was inverted on cued
trials. Four display times were used 80, 115,
150 185ms. The SES was presented 150ms after
the end of the cue
Visual Acuity Task N16 Animals were presented
with cues (100ms presentation time) that differed
in their spatial frequency while maintaining a
constant overall brightness which was the same as
the non-cue background (gray). The SES was
presented 150ms after the end of the cue
Silent Gap N16 A broadband white noise
background was presented. On cued trials there
was a gap (silence) in the white noise 50ms
before the startle burst (SES). The length of
the gap varied from 2-10ms
.
GENERAL METHODS
Subjects - male Wistar rats born to dams ordered
from Charles River, and raised at the Univ. of
Connecticut. Early hypoxic-ischemic (HI) injuries
was induced via a combination of right carotid
artery cauterization followed by 120 minutes
exposure to a hypoxic chamber (8 humidified
oxygen) on postnatal day 7. Startle Attenuation
Paradigm Animals were subjected to either a
cued or uncued loud sound burst (startle
eliciting stimulus or SES). 4 different types of
cues were used, two auditory and two visual. The
degree to which the amount of startle was
affected by the cue served as an index of the
rats ability to perceive the cue.

• SUMMARY CONCLUSIONS
• Individual performance was correlated within a
  task
• Performance was not correlated across tasks even
  within a modality -this indicates these tasks are
  measuring different types of information
  processing
• Processing time was fastest for the silent gap
  task and tended to be longer for the visual tasks
• Degree of startle attenuation was greatest for
  the FM sweep cue, and weakest for the visual cues

Test Apparatus Subjects were placed on a PHM-250
load cell platform. A 50ms burst of white noise
(105-123db) served as the startle eliciting
stimulus (SES), and was played through speakers
placed above the rat. Movement was transformed
into voltage by a load cell and analyzed with
AcqKnowledge (Biopac Inc.) software.
Significant 1-tailed correlation
.
Visual Acuity Cue 1 vs 2
Silent Gap 4 vs. 10ms
An example of the visual testing apparatus with
three LCD screens for displaying the visual
stimuli, a speaker above the animal for
presenting the SES, and the load cell platform
under the animal.
The degree the animals jumped in response to the
SES. Note that early in training there is some
habituation of the startle followed by asymptotic
responding.
Supported by UConn FRS444880 445142 NIH
R29-A613941-01A1
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