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Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation.

Forlim CG, Pinto RD, Varona P, Rodríguez FB - PLoS ONE (2015)

Bottom Line: In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals.Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics.We also discuss the implications of these findings in the context of information processing in weakly electric fish.

View Article: PubMed Central - PubMed

Affiliation: Laboratório Fenômenos Não-Lineares, Instituto de Física, Universidade de São Paulo, São Paulo, Brazil.

ABSTRACT
In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish's own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish.

No MeSH data available.


Setup for closed-loop activity-dependent protocol.A–Experimental Setup. The EODs were measured using 8 electrodes, placed on the bottom of the tank (40×30×25) cm. The electrodes were connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles). The signal from the 5 dipoles were differently amplified (gain = 50x or 100x: for small fish ~5 cm), summed, squared and then digitized at 25kHz by an ADC board (NI PCI-6521) and stored for posterior analysis. The stimulus pulses were generated by the same ADC board and controlled in real time by a closed-loop real time software that detected the EODs timing and delivered stimulus pulses in response. The stimulus pulses were delivered to the tank by a 7 cm dipole (artificial fish) to mimic an average size of Gnathonemus petersii used in this study. The artificial fish was placed in the middle of the tank as shown in the figure. B–Closed-loop activity-dependent protocol. The real time closed-loop software detected the EODs timing and sent a stimulus pulse after a time delay (d) chosen by the experimenter. The stimulus pulses had the exact Gnathonemus petersii waveform and 3V amplitude to mimic an average size animal. All experiments were performed with the same amplitude and wave shape.
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pone.0141007.g001: Setup for closed-loop activity-dependent protocol.A–Experimental Setup. The EODs were measured using 8 electrodes, placed on the bottom of the tank (40×30×25) cm. The electrodes were connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles). The signal from the 5 dipoles were differently amplified (gain = 50x or 100x: for small fish ~5 cm), summed, squared and then digitized at 25kHz by an ADC board (NI PCI-6521) and stored for posterior analysis. The stimulus pulses were generated by the same ADC board and controlled in real time by a closed-loop real time software that detected the EODs timing and delivered stimulus pulses in response. The stimulus pulses were delivered to the tank by a 7 cm dipole (artificial fish) to mimic an average size of Gnathonemus petersii used in this study. The artificial fish was placed in the middle of the tank as shown in the figure. B–Closed-loop activity-dependent protocol. The real time closed-loop software detected the EODs timing and sent a stimulus pulse after a time delay (d) chosen by the experimenter. The stimulus pulses had the exact Gnathonemus petersii waveform and 3V amplitude to mimic an average size animal. All experiments were performed with the same amplitude and wave shape.

Mentions: The experiments were performed in a (40 x 30 x 25) cm tank (30 L) with water temperature at 25°C. To measure the fish's EODs (Fig 1A), 8 silver tip electrodes were placed on the bottom of the tank, 4 at the corners and 4 at half distance (Fig 1A–colored circles), and connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles; as shown in Fig 1A). Signals from the electrodes were differentially amplified (TL082, Texas Instruments; gain = 50x or 100x: for small fish ~5 cm) summed (UA 741, Texas Instruments) and squared (AD633, Texas Instruments). The squared signal was digitized at 25kHz by an ADC board (NI PCI-6521, National Instruments Corporation). Such configuration, adapted from [9] and originally designed to measure the activity of Gymnotus carapo, allows fish of all sizes to have their EODs detected while freely swimming due to an optimal cubic configuration of the electrodes resulting in 7 dipoles and to the fact that the signals measured in each dipole is squared and all 7 squared signals are summed. The setup was adapted to Gnathonemus petersii size and motor activity. Gnathonemus petersii remain most of the time swimming close to the bottom of the tank, so all electrodes were placed at the bottom. Two dipoles were also placed in the middle of the glass walls (B1-B2 and C1-C2 in Fig 1A) instead of in the corners. This configuration reduced the 7 dipole (cubic configuration) to a simpler 5 dipole one but yet keeping its main features. The total number of dipoles in the tank must be chosen as a compromise between the size of the animal and the size of the tank.


Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation.

Forlim CG, Pinto RD, Varona P, Rodríguez FB - PLoS ONE (2015)

Setup for closed-loop activity-dependent protocol.A–Experimental Setup. The EODs were measured using 8 electrodes, placed on the bottom of the tank (40×30×25) cm. The electrodes were connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles). The signal from the 5 dipoles were differently amplified (gain = 50x or 100x: for small fish ~5 cm), summed, squared and then digitized at 25kHz by an ADC board (NI PCI-6521) and stored for posterior analysis. The stimulus pulses were generated by the same ADC board and controlled in real time by a closed-loop real time software that detected the EODs timing and delivered stimulus pulses in response. The stimulus pulses were delivered to the tank by a 7 cm dipole (artificial fish) to mimic an average size of Gnathonemus petersii used in this study. The artificial fish was placed in the middle of the tank as shown in the figure. B–Closed-loop activity-dependent protocol. The real time closed-loop software detected the EODs timing and sent a stimulus pulse after a time delay (d) chosen by the experimenter. The stimulus pulses had the exact Gnathonemus petersii waveform and 3V amplitude to mimic an average size animal. All experiments were performed with the same amplitude and wave shape.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608794&req=5

pone.0141007.g001: Setup for closed-loop activity-dependent protocol.A–Experimental Setup. The EODs were measured using 8 electrodes, placed on the bottom of the tank (40×30×25) cm. The electrodes were connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles). The signal from the 5 dipoles were differently amplified (gain = 50x or 100x: for small fish ~5 cm), summed, squared and then digitized at 25kHz by an ADC board (NI PCI-6521) and stored for posterior analysis. The stimulus pulses were generated by the same ADC board and controlled in real time by a closed-loop real time software that detected the EODs timing and delivered stimulus pulses in response. The stimulus pulses were delivered to the tank by a 7 cm dipole (artificial fish) to mimic an average size of Gnathonemus petersii used in this study. The artificial fish was placed in the middle of the tank as shown in the figure. B–Closed-loop activity-dependent protocol. The real time closed-loop software detected the EODs timing and sent a stimulus pulse after a time delay (d) chosen by the experimenter. The stimulus pulses had the exact Gnathonemus petersii waveform and 3V amplitude to mimic an average size animal. All experiments were performed with the same amplitude and wave shape.
Mentions: The experiments were performed in a (40 x 30 x 25) cm tank (30 L) with water temperature at 25°C. To measure the fish's EODs (Fig 1A), 8 silver tip electrodes were placed on the bottom of the tank, 4 at the corners and 4 at half distance (Fig 1A–colored circles), and connected to form an array of 5 dipoles: R-1R, R-2R and R-3R, sharing a common reference (R; white circles), A1-A2 (yellow circles) and B1-B2 (red circles; as shown in Fig 1A). Signals from the electrodes were differentially amplified (TL082, Texas Instruments; gain = 50x or 100x: for small fish ~5 cm) summed (UA 741, Texas Instruments) and squared (AD633, Texas Instruments). The squared signal was digitized at 25kHz by an ADC board (NI PCI-6521, National Instruments Corporation). Such configuration, adapted from [9] and originally designed to measure the activity of Gymnotus carapo, allows fish of all sizes to have their EODs detected while freely swimming due to an optimal cubic configuration of the electrodes resulting in 7 dipoles and to the fact that the signals measured in each dipole is squared and all 7 squared signals are summed. The setup was adapted to Gnathonemus petersii size and motor activity. Gnathonemus petersii remain most of the time swimming close to the bottom of the tank, so all electrodes were placed at the bottom. Two dipoles were also placed in the middle of the glass walls (B1-B2 and C1-C2 in Fig 1A) instead of in the corners. This configuration reduced the 7 dipole (cubic configuration) to a simpler 5 dipole one but yet keeping its main features. The total number of dipoles in the tank must be chosen as a compromise between the size of the animal and the size of the tank.

Bottom Line: In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals.Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics.We also discuss the implications of these findings in the context of information processing in weakly electric fish.

View Article: PubMed Central - PubMed

Affiliation: Laboratório Fenômenos Não-Lineares, Instituto de Física, Universidade de São Paulo, São Paulo, Brazil.

ABSTRACT
In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish's own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish.

No MeSH data available.