{"id":285,"date":"2016-04-28T20:57:31","date_gmt":"2016-04-28T20:57:31","guid":{"rendered":"http:\/\/labs.la.utexas.edu\/gilden\/?page_id=285"},"modified":"2016-04-28T20:57:57","modified_gmt":"2016-04-28T20:57:57","slug":"gait-and-memory","status":"publish","type":"page","link":"https:\/\/labs.la.utexas.edu\/gilden\/gait-and-memory\/","title":{"rendered":"Gait and Memory"},"content":{"rendered":"

Gait and Memory<\/em><\/strong><\/p>\n

There is a coincidence of time scales between walking and thinking.\u00a0 Memory activation decays on a time interval of about 1.5 seconds (the metronome limit) and gait rhythm has a period of about 1.5 seconds.\u00a0 Either this is an extraordinary coincidence or is a reflection that our memory systems have been tuned to stay active for a gait cycle.\u00a0\u00a0 Coincidences do occur but they are not likely to arise through adaptation.\u00a0 If the time scales are the same it is because there is linkage between moving and hearing.<\/p>\n

In the first place our bodies have a feel to them, we experience our motion not as a series of disconnect efforts, but as a fluid stream.\u00a0 This stream has a lot of structure that depends on what we are doing.\u00a0 When we are walking there is periodicity at all three levels of kinematics; position, velocity, and acceleration.\u00a0 The three levels of periodicity gives walking its feel.\u00a0 Without a clear sense of the walking feeling gait would be an uncoordinated and dangerous endeavor.\u00a0 Anyone who has worked on a motor skill understands the importance of feel.\u00a0 Without feel action is uncoordinated and tentative.<\/p>\n

Feel requires memory activation.\u00a0 Without activation there is no way that our movement would be perceived to be connected.\u00a0 In order for gait to be experienced as connected, motor memory must last over the gait cycle.\u00a0 This is not an issue that has been investigated formally but it seems unlikely that motor activation lasts longer in that successive footfalls seem to create new motor images that overwrite what is currently in memory.\u00a0 In so far as natural terrains (not sidewalks) change subtly with each footfall, it would not be adaptive for walking to generate vivid impressions that extended several steps backwards into the past.\u00a0 One cycle seems like the right amount of activation and gait cycles last for about 1.5 seconds.\u00a0 This is the natural time scale for motor activation to generate the feeling of movement.<\/p>\n

At the same time the cadence of walking generates the feeling of walking, it also creates a soundscape that is pulsing exactly at the gait period.\u00a0 This soundscape is literally a melody made of crunching, snapping, thumping, and scuffling sounds.\u00a0 The same activity generates both a kinesthetic pattern as well as an auditory pattern.\u00a0 They are separately experienced because touch and hearing are distinct modalities, but the information they extract from self-motion is essentially the same.\u00a0 Both modalities are solving a common problem in contour formation and unless there is some specific reason to the contrary, it makes sense that they have the same logic when it comes to putting together discrete moments into patterns.\u00a0 This is essentially the argument for why hearing ended up with activation time scales that are based on gait.<\/p>\n

At a deeper level, the energetics of gait and the experience of temporal patterns both form high-pass filters.\u00a0 A high-pass filter is a device that passes the high frequencies but not the low.\u00a0 Frequency is generally \u201csomething per second\u201d.\u00a0 In music the relevant frequency is the cycles per second of a sound source or the cycles per second of modulator.\u00a0 The same idea is relevant here but now frequency is not cycles per second but the rate at which successive events (notes for example) are provided; literally events per second.\u00a0 In this sense Mr. PC is a high frequency song and Blue Monk is a low frequency song.\u00a0 They are both songs and equally songlike.\u00a0 Mr. PC is just fast sounding and that is a critical part of its aesthetic.\u00a0 From the point of view of contour formation, cognitive limitations are felt principally at the low frequency end, starting at about 30 bpm or \u00bd Hz.\u00a0 This is the effective boundary beyond which successive events lose their coupling.\u00a0 Since there is just one effective boundary we end up with pattern recognition being high-pass instead of band-pass.<\/p>\n

Our bodies also behave as high-pass filters and this can be seen quite clearly in the Rose-Gamble law for energy consumption in walking a unit distance.\u00a0 Energy costs are not the same for fast walking and slow walking.\u00a0 Slow walking is prohibitively expensive as can be seen by the almost vertical ascent of the costs below about 1\/2 meters\/second.\u00a0 There is a hard limit on the low end for the sounds and kinesthetic feel we produce by our own motion.\u00a0 On the fast-walking side of the Rose-Gamble law the energy costs increase at a much slower rate.\u00a0 Efficiency is reduced only by 20% or so when we walk rapidly up to around 3 miles\/hr.\u00a0 What this means practically is that the sweet spot where walking is most effortless is more of a low frequency cut-off than a well-defined and stable minimum.\u00a0 What this means mathematically is that the Rose-Gamble law expresses a filter that passes high frequency motion but not motion much slower than the natural pendulum period of our legs.\u00a0 It is an empirical fact that the mind\u2019s ability to represent temporal structure and the energy required to move the body have the same filtering characteristics.<\/p>\n

Previous: Energy Expense in Gait Produces a Time Scale<\/a>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0Next:\u00a0Perspective<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Gait and Memory There is a coincidence of time scales between walking and thinking.\u00a0 Memory activation decays on a time interval of about 1.5 seconds (the metronome limit) and gait rhythm has a period of about 1.5 seconds.\u00a0 Either this is an extraordinary coincidence or is a reflection that our memory systems have been tuned […]<\/p>\n","protected":false},"author":107,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_uag_custom_page_level_css":"","footnotes":""},"class_list":["post-285","page","type-page","status-publish","hentry","entry"],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false,"site-graphic":false},"uagb_author_info":{"display_name":"ecw255","author_link":"https:\/\/labs.la.utexas.edu\/gilden\/author\/ecw255\/"},"uagb_comment_info":0,"uagb_excerpt":"Gait and Memory There is a coincidence of time scales between walking and thinking.\u00a0 Memory activation decays on a time interval of about 1.5 seconds (the metronome limit) and gait rhythm has a period of about 1.5 seconds.\u00a0 Either this is an extraordinary coincidence or is a reflection that our memory systems have been tuned…","_links":{"self":[{"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/pages\/285","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/users\/107"}],"replies":[{"embeddable":true,"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/comments?post=285"}],"version-history":[{"count":1,"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/pages\/285\/revisions"}],"predecessor-version":[{"id":287,"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/pages\/285\/revisions\/287"}],"wp:attachment":[{"href":"https:\/\/labs.la.utexas.edu\/gilden\/wp-json\/wp\/v2\/media?parent=285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}