tomwalters@0: .TH GENEPN 1 "11 May 1995" tomwalters@0: .LP tomwalters@0: .SH NAME tomwalters@0: .LP tomwalters@0: genepn \- generate excitation pattern tomwalters@0: .LP tomwalters@0: .SH SYNOPSIS tomwalters@0: .LP tomwalters@0: genepn [ option=value | -option ] [ filename ] tomwalters@0: .LP tomwalters@0: .SH DESCRIPTION tomwalters@0: .LP tomwalters@0: Genepn converts the input wave into a simulated neural activity tomwalters@0: pattern (NAP) and summarises the NAP as a sequence of excitation tomwalters@0: patterns (EPNs). The operation takes place in three stages: spectral tomwalters@0: analysis, neural encoding, and temporal integration. In the spectral tomwalters@0: analysis stage, the input wave is converted into an array of filtered tomwalters@0: waves, one for each channel of a gammatone auditory filterbank. The tomwalters@0: surface of the array of filtered waves is AIM's representation of tomwalters@0: basilar membrane motion (BMM) as a function of time (see genbmm). In tomwalters@0: the neural encoding stage, compression, adaptation and, optionally, tomwalters@0: suppression, are used to convert each wave from the filterbank into a tomwalters@0: simulation of the aggregate neural response to that wave. The array of tomwalters@0: responses is AIM's simulation of the neural activity pattern (NAP) in tomwalters@0: the auditory nerve at about the level of the cochlear nucleus (see tomwalters@0: gennap). Finally, the NAP is converted into a sequence of excitation tomwalters@0: patterns (EPNs) by calculating the envelope of the NAP and extracting tomwalters@0: spectral slices from the envelope every 'frstep_epn' ms. The envelope tomwalters@0: is calculated continuously, by lowpass filtering the individual tomwalters@0: channels of the NAP as they flow from the cochlea simulation. tomwalters@0: .LP tomwalters@0: The excitation pattern produced by genepn is intended to simulate the tomwalters@0: spectral representation of a sound as it occurs in the peripheral tomwalters@0: auditory system after neural transduction at about the level of the tomwalters@0: cochlea nucleus. As a result, the frequency resolution of the tomwalters@0: analysis varies with the center frequency of the channel, and the tomwalters@0: distribution of channels across frequency is chosen to match that in tomwalters@0: the auditory system. (For details, see the manual entry for genbmm.) tomwalters@0: The excitaion pattern is a plot of the activity in each channel as a tomwalters@0: function of the centre frequency of the auditory filter that defines tomwalters@0: the channel. In AIM, the suffix 'epn' is used to distinguish this tomwalters@0: spectral representation from the other spectral representations tomwalters@0: provided by the software ('asa' auditory spectral analysis, 'sgm' tomwalters@0: auditory spectrogram, and 'cgm' cochleogram). tomwalters@0: .LP tomwalters@0: The NAP generated by genepn is the same as that produced by gennap. tomwalters@0: The primary differences are in the display defaults and the inclusion tomwalters@0: of the Leaky Integration used to construct the excitation patterns tomwalters@0: from the NAP. As a result, this manual entry is restricted to tomwalters@0: describing the option values that differ from those in gennap and the tomwalters@0: additional options required to control the Leaky Integration. tomwalters@0: .LP tomwalters@0: .SH DISPLAY DEFAULTS tomwalters@0: .LP tomwalters@0: The default values for three of the display options are reset to tomwalters@0: produce a spectral format rather than a landscape. Specifically, tomwalters@0: display=excitation, bottom=0 and top=2500. The number of channels is tomwalters@0: increased to 128 to ensure reasonable frequency resolution in the tomwalters@0: excitation pattern display. tomwalters@0: .LP tomwalters@0: .SH LEAKY INTEGRATION tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: stages_idt tomwalters@0: Number of stages of lowpass filtering tomwalters@0: .RS tomwalters@0: Default unit: scalar. Default value: 2 tomwalters@0: .RE tomwalters@0: .TP 13 tomwalters@0: tup_idt tomwalters@0: The time constant for each filter stage tomwalters@0: .RS tomwalters@0: Default unit: ms. Default value: 8 ms. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: The Equivalent Rectandular Duration (ERD) of a two stage lowpass tomwalters@0: filter is about 1.6 times the time constant of each stage, or tomwalters@0: 12.8 ms in the current case. tomwalters@0: .TP 13 tomwalters@0: frstep_epn tomwalters@0: The time between successive spectral frames tomwalters@0: .RS tomwalters@0: Default unit: ms. Default value: 10 ms. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: With a frstep_epn of 10 ms, genepn will produce tomwalters@0: spectral frames at a rate of 100 per second. tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: downsample tomwalters@0: The time between successive spectral frames. tomwalters@0: .RS tomwalters@0: Default unit: ms. Default value: 10 ms. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: Downsample is simply another name for frstep_epn, provided to tomwalters@0: facilitate a different mode of thinking about time-series data. tomwalters@0: .RE tomwalters@0: .LP tomwalters@0: .LP tomwalters@0: .SH FILES tomwalters@0: .LP tomwalters@0: .TP 13 tomwalters@0: .genepnrc tomwalters@0: The options file for genepn. tomwalters@0: .LP tomwalters@0: .SH SEE ALSO tomwalters@0: .LP tomwalters@0: genasa, gennap, genbmm, gensgm, gencgm tomwalters@0: .LP tomwalters@0: .SH COPYRIGHT tomwalters@0: .LP tomwalters@0: Copyright (c) Applied Psychology Unit, Medical Research Council, 1995 tomwalters@0: .LP tomwalters@0: Permission to use, copy, modify, and distribute this software without fee tomwalters@0: is hereby granted for research purposes, provided that this copyright tomwalters@0: notice appears in all copies and in all supporting documentation, and that tomwalters@0: the software is not redistributed for any fee (except for a nominal tomwalters@0: shipping charge). Anyone wanting to incorporate all or part of this tomwalters@0: software in a commercial product must obtain a license from the Medical tomwalters@0: Research Council. tomwalters@0: .LP tomwalters@0: The MRC makes no representations about the suitability of this tomwalters@0: software for any purpose. It is provided "as is" without express or tomwalters@0: implied warranty. tomwalters@0: .LP tomwalters@0: THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING tomwalters@0: ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL tomwalters@0: THE A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES tomwalters@0: OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, tomwalters@0: WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, tomwalters@0: ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS tomwalters@0: SOFTWARE. tomwalters@0: .LP tomwalters@0: .SH ACKNOWLEDGEMENTS tomwalters@0: .LP tomwalters@0: The AIM software was developed for Unix workstations by John tomwalters@0: Holdsworth and Mike Allerhand of the MRC APU, under the direction of tomwalters@0: Roy Patterson. The physiological version of AIM was developed by tomwalters@0: Christian Giguere. The options handler is by Paul Manson. The revised tomwalters@0: SAI module is by Jay Datta. Michael Akeroyd extended the postscript tomwalters@0: facilites and developed the xreview routine for auditory image tomwalters@0: cartoons. tomwalters@0: .LP tomwalters@0: The project was supported by the MRC and grants from the U.K. Defense tomwalters@0: Research Agency, Farnborough (Research Contract 2239); the EEC Esprit tomwalters@0: BR Porgramme, Project ACTS (3207); and the U.K. Hearing Research Trust. tomwalters@0: