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We explored the effect of deafness on the spatial (gradient) and temporal (decay) properties of oculomotor inhibition of return (IOR) using a task developed by Vaughan (Theoretical and applied aspects of eye movement research. Elsevier, North Holland, pp 143-150, 1984) in which participants made a sequence of saccades to carefully placed targets . Unlike IOR tasks in which ignored cues are used to explore the aftereffects of covert orienting, this task better approximates real-world behavior in which participants are free to make eye movements to potentially relevant inputs. Because IOR is a bias against returning attention and gaze to a previously attended location, we expected to find, and we did find, slower saccades toward previously fixated locations. Replicating Vaughan, a gradient of inhibition around a previously fixated location was observed and this inhibition began to decay after 1200 ms. Importantly, there were no significant differences between the deaf and the normal hearing subjects, on neither the magnitude of oculomotor IOR, nor its decay over time, nor its gradient around the previously fixated location .

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t h x a , NY 14853.AbstractConsider a compound channel W with L component discrete memoryless channels (DMCs). We seek a channel code which serves two purposes: the code must achieve a communication rate Rover every DMC in W , and the decoder must accurately detect which of the DMCs in W is in effect. These two objectives are clearly conflicting: accurate detection of the channel is possible only if the code consists of relatively few codewords; such codes though convey little information. Suppose we measure detection performance using the hypothesis testing error exponent r. We ask the following question: what communication rates R and error exponents r are simultaneously achievable on W? For the case L = 2 and a Neyman-Pearson detection approach, we establish single-letter bounds and prove a strong converse. I. PROBLEM STATEMENTThe transmitter encodes one of M possible messages into one of M blocklength n codewords chosen from X", where X is the channel input alphabet. The codeword x is transmitted through a DMC with output alphabet Y . The DMC has a probability transition matrix given by either Wo(y1z) or Wl(ylz) under the null and alternative hypotheses, respectively. The received codeword y is processed to determine, as accurately a s possible, the transmitted message and the channel hypothesis. A (n, A, e, M , r ) simultaneous communication and detection (CD) code for the compound channel {WO, W I } consists oE 1. A codebook C = {xi E X n : 1 I i 5 M } and an encoder f : (1,. . . , M } --t Xn, such that f (2) 2 xi. set 2. A decoder q5 which maps received words to the message q5 : Y" + (1,. . . , M } . We choose q5 so that 3. A detection or hypothesis testing function 11 0-7803-5000-6/98/$10.00 0 1998 IEEE. Harish Viswanathan Lucent Technologies Bell Labs, HOH L272, 791 Holmdel Rd, Holmdel, NJ 07733. A rate-exponent pair ( R , r ) is said to be (A,€)-achievable if, for every 6 > 0 and all sufficiently large n, there exists a (n, A, E , 2"(R-6), r-6) CD code. A rate-exponent pair (R, r ) is achievable if it is (A, €)-achievable for every 0 < A, E < 1. Let R(A, e) and R be the set of all (A, €)-achievable and achievable rate-exponent pairs, respectively. Now define the exponentrate function A r(R) = sup r. ( R , r ) E a 11. MAIN RESULTS Define Theorem 1 r ( R ) 5 r a ( R ) . Now let P, Q be any distributions on X, and let 0 5 T I 1; for R 2 0, define + (1 -~)~(wollwilQ) + I T W , WO) -RI+, and rL(R) = rE[O.l],P,Q: max rl(.r,P,Q,R) A r z (~, p , Q , R l . Theorem 2 r(R) 2 rL(R). A R l r [ l ( P , W o ) h I ( P , W i )IExcept in special cases, our upper and lower bounds on r(R) do not agree. It is therefore important to prove a strong converse theorem and establish that R ( A , E ) is independent of (A, E ) . Theorem 3 (Strong Converse) LetA p = min W~( y l z ) . Z € X , 1 / E Y If p > 0, then f o r every 0 < A, E < 1, R(A, E ) = R. For proofs of these results, see [l]. REFERENCES[I] S. Jayaraman and H. Viswanathan. "Simultaneous Communication and Detection over Compound Channels"