This paper gives HRTF magnitude data in numerical form for 43 frequencies between 0.2---12 kHz, the average of 12 studies representing 100 different subjects. However, no phase data is included in the tables; group delay simulation would need to be included in order to account for ITD. In 3-D sound applications intended for many users, we want might want to use HRTFs that represent the common features of a number of individuals. But another approach might be to use the features of a person who has desirable HRTFs, based on some criteria. (One can sense a future 3-D sound system where the pinnae of various famous musicians are simulated.) A set of HRTFs from a good localizer (discussed in Chapter 2) could be used if the criterion were localization performance. If the localization ability of the person is relatively accurate or more accurate than average, it might be reasonable to use these HRTF measurements for other individuals. The Convolvotron 3-D audio system (Wenzel, Wightman, and Foster, 1988) has used such sets particularly because elevation accuracy is affected negatively when listening through a bad localizers ears (see Wenzel, et al., 1988). It is best when any single nonindividualized HRTF set is psychoacoustically validated using a 113 statistical sample of the intended user population, as shown in Chapter 2. Otherwise, the use of one HRTF set over another is a purely subjective judgment based on criteria other than localization performance. The technique used by Wightman and Kistler (1989a) exemplifies a laboratory-based HRTF measurement procedure where accuracy and replicability of results were deemed crucial. A comparison of their techniques with those described in Blauert (1983), Shaw (1974), Mehrgardt and Mellert (1977), Middlebrooks, Makous, and Gree...

A motor theory of speech perception, initially proposed to account for results of early experiments with synthetic speech, is now extensively revised to accommodate recent findings, and to relate the assumptions of the theory to those that might be made about other perceptual modes. According to the revised theory, phonetic information is perceived in a biologically distinct system, a ‘module ’ specialized to detect the intended gestures of the speaker that are the basis for phonetic categories. Built into the structure of this module is the unique but lawful relationship between the gestures and the acoustic patterns in which they are variously overlapped. In consequence, the module causes perception of phonetic structure without translation from preliminary auditory impressions. Thus, it is comparable to such other modules as the one that enables an animal to localize sound. Peculiar to the phonetic module are the relation between perception and production it incorporates and the fact that it must compete with other modules for the same stimulus variations.

this article that the choice of a variability model has a major, nontrivial impact on the encoding properties of the neural population. The immense variability of individual response parameters, such as tuning widths or correlation coef#cients, has also been neglected in most previous work. Although these parameter variations are always found in empirical data, they were considered functionally insignificant, and hence theoretical studies have almost always assumed uniform parameters throughout the population. We will show here that this uniform case is unfavorable in the sense that the introduction of parameter variability improves the encoding performance

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We study the problem of statistically correct inference in networks whose basic representations are population codes. Population codes are ubiquitous in the brain, and involve thesimultaneous activity ofmany units coding for some low dimensional quantity. A classic example are place cells in the rat hippocampus: these re when the animal is at a particular place in an environment, so the underlying quantity has two dimensions of spatial location. We show howtointerpret the activity as encoding whole probability distributions over the underlying variable rather then just single values, and propose a method of inductively learning mappings between population codes that are computationally tractable and yet o er good approximations to statistically optimal inference. We simulate the method on some simple examples to prove its competence. In a population code, information about some lowdimensional quantity (such as the position of a visual feature) is represented in the activity of a collection of units, each responding to a limited range of stimuli within this low-dimensional space. Strong evidence exists for this form of coding at the sensory input areas of the brain (eg retinotopic and tonotopic maps) as well as at the motor output level [Georgopoulos et al., 1986]. Evidence is mounting that many other intermediate neural processing areas also use population codes [Tanaka, 1996]. Certain important questions about population codes have been extensively investigated, including how toextract an optimal underlying value [Salinas and Abbott, 1994� Snippe, 1996] and how to learn such representations [Kohonen, 1982]. However, two important issues have been almost ignored (with the important exception of [Anderson, 1994]). One is the treatment of population codes as encoding whole probability density functions (PDFs) over the underlying quantities rather than just a single

The barn owl is a nocturnal hunter, capable of capturing prey using auditory information alone [1]. The neural basis for this localization behavior is the existence of auditory neurons with spatial receptive fields [2]. We provide a mathematical description of the operations performed on auditory input signals by the barn owl that facilitate the creation of a representation of auditory space. To develop our model, we first formulate the sound localization problem solved by the barn owl as a statistical estimation problem. The implementation of the solution is constrained by the known neurobiology.

www.elsevier.com/locate/behavproc The object behind the echo: dolphins (Tursiops truncatus)

Processing of acoustic motion in the auditory cortex of the rufous horseshoe bat, Rhinolophus rouxi

doi: 10.3389/fnhum.2012.00064 Age-related dissociation of sensory and decision-based auditory motion processing