Our brain-body connection has never been so robust. Gut thinking is no simple turn of phrase: microbes in our intestines affect our risk for neurological conditions, and influence our mood and mental health. And when it comes to preventing cognitive decline, physical activity is paramount. The human brain has many more revelations in store, and they may require us to rethink old ideas or correct our assumptions. Standing 1. Over the past millions of years, biologically speaking, the Mediterranean has been a weird place.
Made up of lots of islands spread across multiple archipelagos, some of the lumps of rocks were home to dwarf elephants and hippos, others giant rats and hedgehogs. But one group of islands, in what is now central Italy, had a whole menagerie of giant birds, which grew in formidable size due to the lack of terrestrial predators. These are hard, rounded patches of skin found on the wings, and can deliver a devastating blow. This type of battering behavior can even be found in some modern birds, such as ducks, today. One account even records a male steamer violently biting and beating a shoveler duck to death, causing multiple broken bones and massive internal bleeding.
All the while, the female steamer watched on, calling and displaying to the male. The most likely explanation for the goose's suspected sinister fighting style is competition between males for territories and mates. In addition, responsiveness to the competing tags 3 s after a change appears to be broad rather than selective.
Visual novelty modulates frequency tag power. A Center-surround pattern, with visual changes in the center. B Epochs of behavioral fixation that included a visual change were analyzed for 7 and 9 Hz power. Power for either frequency 3 s after the change were contrasted, as a ratio, with 3 s before the event dashed boxes.
D Novelty events occurring during flight epochs without fixation were analyzed for 7 and 9 Hz power before and after the visual change in the center. LFP power for either frequency 3 s after the change were contrasted, as a ratio, with 3 s before the event dashed boxes. Blue trace: LFP; green line: image position.
G 7 and 9 Hz ratios for novelty events during non-flight epochs, for either tag configuration C, center; S, surround. H The same data as in G was reanalyzed after binning into five separate categories depending on how much time had passed since the last change. A ratio was calculated for either tag, contrasting the 3 s after vs. I 7 Hz blue and 9 Hz red ratios for visual changes during non-flight experiments, binned into 5 temporal groups. Shown are results for 7 Hz center vs. Previous studies in non-flying Drosophila have shown that the magnitude of visual novelty effects depend on how much time has elapsed before an image changes van Swinderen, b ; van Swinderen and Brembs, Does object shape matter?
Previous studies have shown that vertical bars are attractive in a similar paradigm Maimon et al. A different question was whether the novelty salience effects depended on where changes happened in the fly's visual field. For example, a change occurring behind the fly where it cannot be seen might not be as salient as a change happening in front of the fly, which might be startling. Together, these more detailed analyses of one frequency tag 7 Hz center indicate that responsiveness in the brain LFP depends on elapsed time between novelty events.
Object shape, novelty location, and image velocity modulate visual salience effects.
ataphlimar.ga: The Flightless Mind Observed (): Lynn Hendricks, Grace Brooks: Books. A trio of whimsical tales and light verse, illustrated in a variety of styles to give each story a life of its own. The Flightless Mind Observed offers a Victorian artist's .
Only 7 Hz effects are shown. Rose plots on left indicate positions where changes occurred for either set of experiments. One possibility is that it is not absolute time that is critical here, but rather the stimulus presentation rate in this particular paradigm. In the faster scenario 1.
This supports the possibility that pattern speed, rather than absolute time, determines the differential responses to the central object. In the preceding analyses I contrasted LFP responses to competing flicker before and after a visual change. I next investigated ongoing responses to competing flicker following a visual change. These analyses thus queried what happened to 7 and 9 Hz power during the entire 40 s after the last change. One interpretation of these results would suggest that when 7 Hz is dominant, flies are attending to the moving center, while suppressing the adjacent surround that is moving with it.
Central to this interpretation is the notion that the fly is then actively attending to the flickering object as it moves, and therefore primed to respond at that time to any changes in the center. Ongoing frequency tag dynamics are tied to pattern velocity. The number of rotations is indicated below the time axis. The approximate number of rotations for either image velocity condition is indicated by matching color below the time axis. E A model of the spatio-temporal dynamics of LFP frequency tag effects following a visual change in the center red bar.
The angle subtended by the different object components surround, area inside surround, and center is indicated. To further investigate whether these attention-like effects are tied to the pattern presentation rate rather than absolute time, the same analyzes were done on experiments where the image rotation speed was slowed down to a 4—4.
This study shows that LFP responses to visual flicker in the fly brain depend on behavioral state as well stimulus history and salience, suggesting that endogenous mechanisms in the fly brain are modulating synchronized neuronal responses to visual flicker. By presenting competing flickering stimuli to Drosophila , it should in principle be possible to study mechanisms of visual attention in the insect brain using paradigms traditionally used in human attention research.
Indeed, the frequency-tagging approach used in this study to track attention-like behavior in flies was inspired from similar approaches applied to study human attention Vialatte et al. Frequency tags also termed steady-state visually evoked potentials, SSVEPs provide common neurophysiological indices of attention that are equally accessible in both human subjects and animal models. However, the use of animal models allows more invasive techniques, such as genetic manipulation, to be applied in order to probe the underlying neurobiology of the response Paulk and van Swinderen, in preparation.
Surprisingly, SSVEPs have rarely been used to study visual attention in animals other than primates, possibly because few paradigms allow for brain recordings in restrained animals still capable of demonstrating visual-behavioral choices Miller et al. One of the more striking results from the current study is that changes in frequency tag power in the fly brain associated with visual salience do not have to be associated with active behavior. Although behavior is crucial for supporting conclusions drawn about the relevance of frequency tags to attention, behavior is not a requirement for attention-like processes in human brains Vialatte et al.
We have come to a similar conclusion in previous work focused on endogenous oscillations associated with attention-like process in the fly van Swinderen and Greenspan, ; van Swinderen, a , b ; van Swinderen et al. The fact that attention without any associated behavior modulates visual responsiveness in human brain activity has been known and studied for a long time Hillyard and Anllo-Vento, ; Vialatte et al.
Indeed, even simple animals such as flies show increased responsiveness of visual neurons when they are actively walking Seelig et al. In this study, I show that behavioral fixation in flies increases LFP responses to frequency-tagged visual stimuli, but that such effects can also be evoked in non-flying animals by visual changes, and that LFP responsiveness to competing stimuli appears to alternate in a rivalry-like manner. Visual salience and behavioral fixation effects support the idea that such frequency-tag alternations in the fly brain might be relevant to selective attention.
These data suggest that wild-type flies are attending to restricted parts of their visual field at specified times, and hence more likely to detect any change occurring within the attended area at those times. In human studies, a spotlight metaphor is often used to describe attention processes LaBerge, , partially because that is how attention feels to our conscious minds.
This alternation may represent a form of perceptual rivalry in the fly brain, where the focus of attention expands and contracts in accordance with the rate of change occurring around the animal. This raises the question of why an animal might need the capacity to alternate between multiple stimuli, or even to periodically switch among different motor programs [see Maye et al.
Viewed from an evolutionary perspective, it is not difficult to imagine that searching for food, mates, or predators could benefit from rapid and flexible disambiguation of conflicting visual, auditory, and olfactory stimuli or from discriminating figure and ground, in the case of vision. Similarly, being unable to engage or disengage each alternative with appropriate flexibility could also be disadvantageous, suggesting an interaction between memory mechanisms and rivalry rates.
Selective attention is likely tuned to the rate of change in the environment, and this appears to be the case for miniature brains as well as human brains. Maladaptive behavior apparent in a variety of human cognitive disorders, such as schizophrenia, or in key Drosophila mutants proposed as models for these disorders van Alphen and van Swinderen, , may result in part from a failure to match endogenous attention processes to the pace of a continuously changing and moving environment.
Access to ongoing attention-like dynamics in the malleable Drosophila brain, by using competing frequency tags, should reveal how brains select and suppress stimuli to maintain appropriate responsiveness levels and behavior in a visually complex environment. The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
I thank Angelique Paulk for discussions on the frequency tag approach, and for help with brain imaging. The author declares no competing financial interests.
The frequency tag. A Recording sites in the Drosophila brain arrows. Texas Red dye was released from glass recording electrodes by iontophoresis, and the two recording sites determined by the region with greatest staining intensity, in the inner optic lobe. A differential recording was made between these sites.
glanmolighwah.tk The response for a full rotation of the stimulus is shown. F Differential recordings to the thorax reveal the contribution from either optic lobe.
Coherence to the signal is weaker for the within-brain differential, indicating a different quality response than for each individual optic lobe. Data in the paper are all voltage differentials within the brain blue. Frequency tag dynamics in females, and in relation to another tag frequency in the surround. A Log-ratio for 7 Hz center vs. B Log-ratio for 7 Hz vs. National Center for Biotechnology Information , U. Journal List Front Integr Neurosci v. Front Integr Neurosci.