discrete fast fourier transform (nfft) algorithm  (MathWorks Inc)

Journal: Journal of Neurophysiology

Article Title: Envelope contributions to the representation of interaural time difference in the forebrain of barn owls

doi: 10.1152/jn.01166.2015

Figure Lengend Snippet: Frequency-response functions and phase difference spectra. A–H: frequency-response functions of the 8 example neurons shown in Fig. 5 (black solid lines). Error bars give SE of the change in spike rate. Gray dashed lines represent the power spectrum of the neurons’ NDF0. Power and phase spectra were computed with a discrete Fourier transformation. The 1/3 magnitude level of the frequency spectra is marked by the black dotted line. Only those parts of the power spectrum that exceeded the 1/3 magnitude threshold were considered to carry energy. I–P: phase difference spectra of the same 8 example neurons (black lines). Phase difference spectra were created by subtracting the phase spectrum of the NDF180 from the phase spectrum of the NDF0. A phase difference of ±180 indicates phase sensitivity (dotted lines), while a phase difference of 0 or 360 indicates phase invariance.

Article Snippet: Phase and power spectra of the NDFs were calculated with a step size of 256 Hz using a discrete Fourier transformation algorithm (fft, MATLAB; MathWorks).

Techniques: Transformation Assay

Journal: Journal of Neurophysiology

Article Title: Envelope contributions to the representation of interaural time difference in the forebrain of barn owls

doi: 10.1152/jn.01166.2015

Figure Lengend Snippet: AAr responses to high-pass filtered noise. A–D: NDF0 (black lines) and NDF180 (gray dashed lines) of the 4 neurons shown in Fig. 5, A, D, F, and H. NDFs were recorded using high-pass filtered noise stimuli. Upper and lower envelope functions are shown as black dotted lines. Delay asymmetry (delA) and correlation coefficients (r) are given at top left of each panel. The cutoff frequency for the high-pass noise stimuli was chosen individually for each neuron depending on its frequency response function (compare Fig. 10). Cutoff frequencies ranged from 2.5 to 5.5 kHz. E–H: cross-correlation functions of the NDF envelope functions shown in A–D (black lines). The position of the cross-correlation’s minimum determines the neurons delay asymmetry. Gray lines depict the cross-correlation functions of the min and max functions (not shown; see Fig. 2). I–L: power spectra of the NDF0 shown in A–D. Power spectra were computed with fast Fourier transformation algorithm.

Article Snippet: Phase and power spectra of the NDFs were calculated with a step size of 256 Hz using a discrete Fourier transformation algorithm (fft, MATLAB; MathWorks).

Techniques: Transformation Assay