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Glossary


AC Coupled Amplification: Amplification of only AC components of a signal. The DC component (DC offset) is blocked by a capacitor/resistor network in the input signal path. AC coupled amplification is the alternative to DC Coupled Amplification.

Amplitude: Amplitude of a given position in an EOD waveform. Amplitude is displayed in arbitrary units (not representing voltage of discharge) intended for comparative purposes only. These values are scaled to a Peak-to-Peak Amplitude defined by a user-defined Scale Factor.

Area: Area under the curve of an EOD waveform calculated as the Integral of Duration (ms) and Amplitude .

Baseline: the resting amplitude value between successive EODs. In Pulse-Type Electric fish the baseline usually (but not always) corresponds to the Zero Line (0V). In some circumstances there may be a natural DC Offset to the signal. The baseline may also depart from the zero line if the digitizing software does not center bipolar signals at 0V (as is the case for PC99 Files or some files digitized with DC Coupled Amplification ).

Cubic Spline Interpolation: A procedure for the determination of intermediate Amplitude and Duration values between successive Sample Points in a Data Array . Cubic Spline Interpolation determines the position of intermediate points by computing a theoretical curve through sampling points. A cubic spline is a piecewise cubic polynomial such that the function, its derivative and its second derivative are continuous at the interpolation nodes. Electric Fish Waveform Analyzer uses a cubic spline algorithm based on Bezier curves.

Data Array: A vertical column (array) of Sample Points , each with a specific Amplitude and a known Sampling Frequency is the raw data used to plot and analyze EOD waveforms in the Electric Fish Waveform Analyzer program.

DC Coupled Amplification: Amplification of all components of a signal down to direct current (0 Hz or “DC”). DC coupled amplification preserves the DC offset of a signal. DC coupled amplification is the alternative to AC Coupled Amplification .

DC offset: (DC = direct current). Appears in signal recordings with DC Coupled Amplification as a natural departure of the Baseline of an EOD from the Zero Line (0V) associated with a slow flow of current through the electric organ (creating an offset voltage).

Derivative: The derivative of the EOD is computed at each Sample Point as dy/dx (change in Amplitude (y) / change in Duration (x)) between that sampling point and the previous one.

Duration: The duration (in milliseconds, ms) between two points in an EOD waveform. Electric Fish Waveform Analyzer measures duration of Phases and Segments of phases.

Electric Fishes: Fish that generate Weakly Electric or Strongly Electric Electric Organ Discharges (EODs). The most diverse groups of electric fish are the New World Gymnotiform fishes and the Old World Mormyriform fishes. Other electrogenic fish groups include the African freshwater catfishes (Malapterus), the marine rays (Torpedo) and the stargazers (Uranoscopidae).

Electric Organ Discharge (see EOD)

End: The position of the end of the EOD at a user defined % amplitude (see Analyze Waveform Shape) of the last Phase.

EOD (= Electric Organ Discharge). The external electric field generated from the discharge of one or more electric organs in Electric Fishes . In Pulse-Type electric fish the terms EOD, EOD waveform and Waveform refer (in this help system) interchangeably to a single pulse. In Tone-Type electric fish the terms EOD, EOD waveform and Waveform refer (in this help system) to a sequence of variable length which includes at least two positive wave crests and their intervening troughs.

Fourier Power Spectrum: Frequency domain plot showing the frequency composition of an EOD. Here the horizontal deflection is the frequency variable and the vertical deflection is the signals amplitude at that frequency. Frequency is displayed on a linear scale as kHz (kilohertz). Amplitude is displayed on a logarithmic scale as dB (decibels). Each –3dB attenuation from the minimum attenuation at 0 dB represents an approximate halving of signal amplitude. The peak frequency in the Fourier Power Spectrum (scaled to the minimum attenuation of 0 dB) is the Peak Power Frequency (PPF ). Fourier Power Spectra are computed using a 2048-point Fast Fourier Transform (FFT). The FFT is a mathematical procedure originally developed by the French mathematician John Baptiste Fourier (1768 – 1830).

Gymnotiform: New World Electric Fishes of the order Gymnotiformes (Teleostei: Ostariophysi). Weakly Electric Gymnotiforms are known by many names, e.g.: knife-fishes [English]; sarapó, itui [Portuguese - Brazil]; macana [Spanish - Peru]; cuchillo [Spanish - Venezuela, Colombia]). The Strongly Electric gymnotiform, Electrophorus electricus, is known as the electric eel [English], poraquê [Portuguese – Brazil], anguila electrica [Spanish], temblador [Spanish-Venezuela].

Integral: Area under the curve of the EOD Waveform. Integration is based on computing the area between successive Sample Points . The area between two samples (above or below the Zero Line ) is approximated by the sum of the area of:

i. a rectangle between samples bordered at one end by the zero line and at its opposite end by the lowest amplitude of the two samples.

ii. a right-angled triangle whose hypotenuse forms a straight line between the sample points and which sits on top of (or below for –ve phases) the rectangle.


Interpolation: Process of determining intermediate position between a series of Sample Points . Triangulation Interpolation draws a straight line between sample points. Cubic Spline Interpolation draws a curved line between sample points.

Offset: Disparity between amplitude of Baseline of an EOD waveform and the Zero Line (true 0 volts).

P1: The dominant positive Phase of a Pulse-Type EOD plotted with head positivity upwards. P1 can also be applied to the dominantly positive component of a Tone-Type EOD.

P1 + P2 Amplitude: Amplitude difference between Peak Amplitude of Phases P1 and P2.

PC99 Files: Files that were digitized and saved in .prn (Lotus TM) format using the Amplicon PC99 TM Analog-Digital acquisition hardware and software. Any column-arranged array of amplitude readings recorded at a known Sampling Frequency can be converted to PC99 file format using a text editor or spreadsheet program using the file format described in PC99 Files.

Peak Amplitude: Maximum amplitude of a given Phase of an EOD.

Peak Power Frequency: (PPF). The Frequency in the Fourier Power Spectrum of an EOD with the greatest amplitude value. PPF is scaled to the minimum attenuation of 0 dB.

Peak-to-Peak Amplitude Difference between positive and negative Peak Amplitude of greatest values in an EOD waveform.

Phase: Positive or Negative component of EOD waveform separated by Zero Crossovers. EOD waveforms of gymnotiforms comprise 1 – 6 phases of alternating polarity. The Duration , Amplitude and Area of each phase is variable.

PPF: = Peak Power Frequency of Fourier Power Spectrum of an EOD waveform.

Pulse-Type (EODs/Electric Fishes): EODs comprising a train of discrete pulses separated by silence. Gymnotiform fishes of the families Gymnotidae, Hypopomidae and Rhamphichthyidae generate Pulse-Type EODs. Pulse-Type EODs of gymnotiform fishes comprise from 1 (monophasic) to 6 (multiphasic) Phases of alternating polarity.

Sample Points: Points in an EOD waveform that represent a discrete amplitude recorded during the digitization of the EOD. In an EOD digitized at a Sampling Frequency of 100 kHz (100,000 sample points per second), the time interval separating successive sample points is 1/100,000 = 0.00001 s or 0.01 ms. A vertical column (array) of sample points, each with a specific amplitude and a known sampling frequency is the raw data used to plot and analyze EOD waveforms in the Electric Fish Waveform Analyzer program. Electric Fish Waveform Analyzer operates with a Data Array of 2048 sample points (i.e. 2048 rows of amplitude values).

Sampling Frequency: (also known as sampling rate): The number of Sample Points recorded per unit time by the digitizing device used to record an EOD. In an EOD digitized at a sampling frequency of 100 kHz (100,000 sample points per second), the time interval separating successive sample points is 1/100,000 = 0.00001 s or 0.01 ms.

Sampling Resolution: Resolution of digitised signal in Bits (usual sampling resolutions are 8-bit, 12-bit, 16-bit, 24-bit and 32-bit. The vertical deflection of a signal recorded with 8-bit resolution is represented by only 256 points. With 12-bot resolution this rises to 1024 points. With higher resolutions each sampling point is measured very accurately. With lower resolutions, the measurements are less exact and gentle curves adopt a step-like structure.

Segment: Homologous sections of the Waveform of an EOD following a three-step process of subdivision: 1, separation of up to 5 Phases (P-1, P0, P1 , P2, P3 in strict chronological order) at Zero Crossovers , where P1 is the dominant positive phase in EODs plotted with head-positivity upwards; 2, division of each EOD phase at the phase peak (Peak Amplitude ) into ascending and descending limbs; 3, division of each limb by the position of the maximum positive or negative Derivative value (for ascending and descending phases respectively). Following this procedure a monophasic EOD will have 4 (1 x 4) segments, a biphasic EOD will have 8 (2 x 4) segments and a 6-phase EOD will have (6 x 4) 24 segments, etc.

Sound Files: Files that are stored in .txt format compatible with the commercial sound editing program CoolEdit TM. The Electric Fish Waveform Analyzing program can convert PC99 Files to Sound files. Any column-arranged array of amplitude readings recorded at a known Sampling Frequency can be converted to sound file format using a text editor or spreadsheet program using the file format described in: Sound Files.

Start: The position of the beginning of the EOD at a user defined % amplitude (see Analyze Waveform Shape) of the first Phase.

Strongly Electric (EODs ): EODs with a high voltage - usually exceeding 50 V. Strongly electric EODs are generated by the New World freshwater electric eel Electrophorus electricus, the African freshwater catfish Malapterus electricus, and the marine ray Torpedo spp.

Timing: Absolute Time of an event in an EOD Waveform (relative to the Start of an EOD ).

Tone-Type (EODs/Electric Fishes): EODs comprising a continual periodic wave of alternating polarity with no periods of silence. Gymnotiform fishes of the families Sternopygidae and Apteronotidae generate Tone-type EODs.

Triangulation Interpolation: A procedure for the determination of intermediate Amplitude and Duration between successive Sample Points in a Data Array . Triangulation Interpolation determines the position of intermediate points by plotting a straight line between successive sample points.

Valid Phase: A valid phases is a Phase where the Peak Amplitude exceeds the Minimum Peak %. Only the Duration and Area of valid phases are computed for data output. Valid phases are marked on the EOD plot with Peaks. Invalid phases are not marked.

Waveform: Two-dimensional plot (amplitude on y axis, time on x axis) of a signal, in this case the Electric Organ Discharge (EOD) of an Electric Fish. Used also to refer to the entire array of Sample Points characterizing a digitized signal (including electrical silence flanking the EOD).

Weakly Electric (EODs):EODs with a low voltage (usually less than 1 volt), which cannot be felt but are easily detected and recorded with submerged electrodes and an amplifier. Weakly electric EODs are generated by all New World Gymnotiformes except the strongly electric eel Electrophorus electricus, and all Old World Mormyriformes. All fishes generating weakly electric EODs are from freshwaters.

Zero Crossover: The zero volt (arbitrary amplitude value = 0) boundary between two successive Phases of an EOD.

Zero Line: Line representing a true voltage value of zero (displayed in Electric Fish Waveform Analyzer as an arbitrary amplitude value of zero). The Baseline of an EOD may be Offset from the Zeroline.

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