Cross Modal Sensory Processing Assessments in Rodents

1. Attenuated Startle (%) Attenuated Startle (%) Attenuated Startle (%) Attenuated Startle (%) 80ms 115ms 150ms 185ms Cue type Oddball cue display time Silent Gap (ms) FM Sweep ISI (ms) Cue Auditory or Visual cue-burst interval Cued trial: Uncued trial: Time 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) N=16 A linear frequency downward sweep (2300Hz to 1900Hz, @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 Acuity Task N=16 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 Visual Odd Ball N=6 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 Silent Gap N=16 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 rat’s 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 REFERENCES 1. Peiffer AM, McClure MM, Threlkeld SW, Rosen GD, Fitch RH,(2004). Severity of focal microgyria and associated rapid auditory processing deficits.Neuroreport. 15(12):1923-6. 2.Fitch RH, Tallal P,(2003).Neural mechanisms of language-based learning impairments: insights from human populations and animal models.Behav Cogn Neurosci Rev. 2(3):155-78. 3.Friedman JT, Peiffer AM, Clark MG, Benasich AA, Fitch RH,(2004). Age and experience-related improvements in gap detection in the rat.Brain Res Dev Brain Res.152(2):83-91. 4. Campeau, S.; Davis, M, (1995).Prepulse inhibition of the acoustic startle reflex using visual and auditory prepulses: disruption by apomorphine .Psychopharmacology (Berl) 117 (3): 267-74.