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Competing visual flicker reveals attention-like rivalry in the fly brain.

van Swinderen B - Front Integr Neurosci (2012)

Bottom Line: There is increasing evidence that invertebrates such as flies display selective attention (van Swinderen, 2011a), although parallel processing of simultaneous cues remains difficult to demonstrate in such tiny brains.Local field potential (LFP) activity in the fly brain is associated with stimulus selection and suppression (van Swinderen and Greenspan, 2003; Tang and Juusola, 2010), like in other animals such as monkeys (Fries et al., 2001), suggesting that similar processes may be working to control attention in vastly different brains.Visual competition dynamics in the fly brain were dependent on the rate of pattern presentation, suggesting that attention-like switching in insects is tuned to the pace of visual changes in the environment rather than simply the passage of time.

View Article: PubMed Central - PubMed

Affiliation: Queensland Brain Institute, The University of Queensland Brisbane, QLD, Australia.

ABSTRACT
There is increasing evidence that invertebrates such as flies display selective attention (van Swinderen, 2011a), although parallel processing of simultaneous cues remains difficult to demonstrate in such tiny brains. Local field potential (LFP) activity in the fly brain is associated with stimulus selection and suppression (van Swinderen and Greenspan, 2003; Tang and Juusola, 2010), like in other animals such as monkeys (Fries et al., 2001), suggesting that similar processes may be working to control attention in vastly different brains. To investigate selective attention to competing visual cues, I recorded brain activity from behaving flies while applying a method used in human attention studies: competing visual flicker, or frequency tags (Vialatte et al., 2010). Behavioral fixation in a closed-loop flight arena increased the response to visual flicker in the fly brain, and visual salience modulated responses to competing tags arranged in a center-surround pattern. Visual competition dynamics in the fly brain were dependent on the rate of pattern presentation, suggesting that attention-like switching in insects is tuned to the pace of visual changes in the environment rather than simply the passage of time.

No MeSH data available.


Related in: MedlinePlus

Visual competition. (A) A 30°-wide “X,” composed of 20 LED pixels flickering together at 7 or 9 Hz, was positioned above a centrally-positioned cross (as in Figure 1), also flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz top, 7 Hz center; red, reversed tags). (B) Flies were able to fixate on this compound object (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (C) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (D) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (NF, blue, not flying; Fly, yellow, flight without fixation; Fix, red, flight with fixation) when 7 Hz is center and 9 Hz is top. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, **P < 0.01, ***P < 0.001 by t-test. 9 Hz and 7 Hz groups were significantly different (P < 0.01, by ANOVA), as indicated (upper brackets). The same flies contributed to both sets of data (left and right panels). (E) The cross surrounded by a field of 16 LED dots, subtending 90°, flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz surround, 7 Hz center; red, reversed tags). (F) Flies were able to fixate on this compound stimulus (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (G) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (H) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (as in D) when 7 Hz is center and 9 Hz is the surround. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, by t-test. The same flies contributed to both sets of data (left and right panels).
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Figure 2: Visual competition. (A) A 30°-wide “X,” composed of 20 LED pixels flickering together at 7 or 9 Hz, was positioned above a centrally-positioned cross (as in Figure 1), also flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz top, 7 Hz center; red, reversed tags). (B) Flies were able to fixate on this compound object (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (C) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (D) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (NF, blue, not flying; Fly, yellow, flight without fixation; Fix, red, flight with fixation) when 7 Hz is center and 9 Hz is top. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, **P < 0.01, ***P < 0.001 by t-test. 9 Hz and 7 Hz groups were significantly different (P < 0.01, by ANOVA), as indicated (upper brackets). The same flies contributed to both sets of data (left and right panels). (E) The cross surrounded by a field of 16 LED dots, subtending 90°, flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz surround, 7 Hz center; red, reversed tags). (F) Flies were able to fixate on this compound stimulus (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (G) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (H) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (as in D) when 7 Hz is center and 9 Hz is the surround. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, by t-test. The same flies contributed to both sets of data (left and right panels).

Mentions: Visual stimuli were controlled using custom-written Labview software (National Instruments), as described previously (van Swinderen and Greenspan, 2003; van Swinderen, 2007b). To create visual flicker, images alternated between a blank template of the 72 × 24 LEDs and a frame of the lit image for the object involved, and altering the delay for either frames controlled flicker rate. The visual stimulus was captured by a photodiode in the arena (See Figure A1), this signal was recorded at 300 Hz, and Fourier analysis of the signal confirmed the flicker frequency. Stationary flicker produced much less of a response (Figure A1), so was not used for this study. Different flicker frequencies could be superimposed on the same 72 × 24 LED panorama, thereby creating the dual-flicker compound objects used in this study. Since frequency combinations above 10 Hz proved unreliable (they did not produce those exact, separable frequencies in the LED arena, because of limitations in the Labview updates), a combination of 7 and 9 Hz was used for most experiments, unless specified otherwise (see Figure A1 for other frequency examples). More detailed spectral analysis of these separate and combined signals revealed the flicker rate to actually be 6.5 and 8.9 Hz. No differences in the results were found by simplifying the analyses to 7 and 9 Hz throughout the study. The stimulus used was either a “+” or an “×,” each subtending 30° (square) of the arena, and exactly 20 LED pixels. The cross or “×” was centrally positioned in the arena, such that it occurred in the fly's lower visual field (flies were angled ~20° up from horizontal). Competing stimuli consisted an “×” positioned over a “+” flickering at a distinct frequency (as in Figure 2A), or of 16 single pixels arranged around the central object (as in Figure 2E), also flickering at a distinct frequency. In the second scenario, the surround therefore created a 70°—wide window around the 30° central object. To study the effect of novelty and time, the central object alternated between a “+” and the “×,” while the surround remained unchanged. Alternation times were drawn from a random number generator, between 5 s and 50 s, and each experiment lasted approximately 700 s, during which on average ~25 changes occurred. Analyses of LFPs after a visual change were done only after a 100 ms delay, to prevent any flicker artifact associated with the switch between objects. These LFP data were contrasted (as a ratio) to data in the same frequency domain before a change, to determine whether there were any novelty salience effects.


Competing visual flicker reveals attention-like rivalry in the fly brain.

van Swinderen B - Front Integr Neurosci (2012)

Visual competition. (A) A 30°-wide “X,” composed of 20 LED pixels flickering together at 7 or 9 Hz, was positioned above a centrally-positioned cross (as in Figure 1), also flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz top, 7 Hz center; red, reversed tags). (B) Flies were able to fixate on this compound object (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (C) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (D) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (NF, blue, not flying; Fly, yellow, flight without fixation; Fix, red, flight with fixation) when 7 Hz is center and 9 Hz is top. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, **P < 0.01, ***P < 0.001 by t-test. 9 Hz and 7 Hz groups were significantly different (P < 0.01, by ANOVA), as indicated (upper brackets). The same flies contributed to both sets of data (left and right panels). (E) The cross surrounded by a field of 16 LED dots, subtending 90°, flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz surround, 7 Hz center; red, reversed tags). (F) Flies were able to fixate on this compound stimulus (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (G) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (H) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (as in D) when 7 Hz is center and 9 Hz is the surround. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, by t-test. The same flies contributed to both sets of data (left and right panels).
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Figure 2: Visual competition. (A) A 30°-wide “X,” composed of 20 LED pixels flickering together at 7 or 9 Hz, was positioned above a centrally-positioned cross (as in Figure 1), also flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz top, 7 Hz center; red, reversed tags). (B) Flies were able to fixate on this compound object (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (C) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (D) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (NF, blue, not flying; Fly, yellow, flight without fixation; Fix, red, flight with fixation) when 7 Hz is center and 9 Hz is top. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, **P < 0.01, ***P < 0.001 by t-test. 9 Hz and 7 Hz groups were significantly different (P < 0.01, by ANOVA), as indicated (upper brackets). The same flies contributed to both sets of data (left and right panels). (E) The cross surrounded by a field of 16 LED dots, subtending 90°, flickering at 7 or 9 Hz. Sample power spectrum is shown in the lower panel (green, 9 Hz surround, 7 Hz center; red, reversed tags). (F) Flies were able to fixate on this compound stimulus (dashed line shows frontal position), in either frequency combination (red vs. green, as indicated). (G) Ongoing analysis of 7 and 9 Hz power during fixation in a sample fly. (H) Left panels: Log-normalized 7 or 9 Hz power (± SEM) for the three behavioral states (as in D) when 7 Hz is center and 9 Hz is the surround. Right panels, the same with swapped frequency tags. n = 6 male wild-type flies; *P < 0.05, by t-test. The same flies contributed to both sets of data (left and right panels).
Mentions: Visual stimuli were controlled using custom-written Labview software (National Instruments), as described previously (van Swinderen and Greenspan, 2003; van Swinderen, 2007b). To create visual flicker, images alternated between a blank template of the 72 × 24 LEDs and a frame of the lit image for the object involved, and altering the delay for either frames controlled flicker rate. The visual stimulus was captured by a photodiode in the arena (See Figure A1), this signal was recorded at 300 Hz, and Fourier analysis of the signal confirmed the flicker frequency. Stationary flicker produced much less of a response (Figure A1), so was not used for this study. Different flicker frequencies could be superimposed on the same 72 × 24 LED panorama, thereby creating the dual-flicker compound objects used in this study. Since frequency combinations above 10 Hz proved unreliable (they did not produce those exact, separable frequencies in the LED arena, because of limitations in the Labview updates), a combination of 7 and 9 Hz was used for most experiments, unless specified otherwise (see Figure A1 for other frequency examples). More detailed spectral analysis of these separate and combined signals revealed the flicker rate to actually be 6.5 and 8.9 Hz. No differences in the results were found by simplifying the analyses to 7 and 9 Hz throughout the study. The stimulus used was either a “+” or an “×,” each subtending 30° (square) of the arena, and exactly 20 LED pixels. The cross or “×” was centrally positioned in the arena, such that it occurred in the fly's lower visual field (flies were angled ~20° up from horizontal). Competing stimuli consisted an “×” positioned over a “+” flickering at a distinct frequency (as in Figure 2A), or of 16 single pixels arranged around the central object (as in Figure 2E), also flickering at a distinct frequency. In the second scenario, the surround therefore created a 70°—wide window around the 30° central object. To study the effect of novelty and time, the central object alternated between a “+” and the “×,” while the surround remained unchanged. Alternation times were drawn from a random number generator, between 5 s and 50 s, and each experiment lasted approximately 700 s, during which on average ~25 changes occurred. Analyses of LFPs after a visual change were done only after a 100 ms delay, to prevent any flicker artifact associated with the switch between objects. These LFP data were contrasted (as a ratio) to data in the same frequency domain before a change, to determine whether there were any novelty salience effects.

Bottom Line: There is increasing evidence that invertebrates such as flies display selective attention (van Swinderen, 2011a), although parallel processing of simultaneous cues remains difficult to demonstrate in such tiny brains.Local field potential (LFP) activity in the fly brain is associated with stimulus selection and suppression (van Swinderen and Greenspan, 2003; Tang and Juusola, 2010), like in other animals such as monkeys (Fries et al., 2001), suggesting that similar processes may be working to control attention in vastly different brains.Visual competition dynamics in the fly brain were dependent on the rate of pattern presentation, suggesting that attention-like switching in insects is tuned to the pace of visual changes in the environment rather than simply the passage of time.

View Article: PubMed Central - PubMed

Affiliation: Queensland Brain Institute, The University of Queensland Brisbane, QLD, Australia.

ABSTRACT
There is increasing evidence that invertebrates such as flies display selective attention (van Swinderen, 2011a), although parallel processing of simultaneous cues remains difficult to demonstrate in such tiny brains. Local field potential (LFP) activity in the fly brain is associated with stimulus selection and suppression (van Swinderen and Greenspan, 2003; Tang and Juusola, 2010), like in other animals such as monkeys (Fries et al., 2001), suggesting that similar processes may be working to control attention in vastly different brains. To investigate selective attention to competing visual cues, I recorded brain activity from behaving flies while applying a method used in human attention studies: competing visual flicker, or frequency tags (Vialatte et al., 2010). Behavioral fixation in a closed-loop flight arena increased the response to visual flicker in the fly brain, and visual salience modulated responses to competing tags arranged in a center-surround pattern. Visual competition dynamics in the fly brain were dependent on the rate of pattern presentation, suggesting that attention-like switching in insects is tuned to the pace of visual changes in the environment rather than simply the passage of time.

No MeSH data available.


Related in: MedlinePlus