Deriving Motor Primitives Through Action Segmentation

Abstract

The purpose of the present experiment is to further understand the effect of levels of processing (top-down vs. bottom-up) on the perception of movement kinematics and primitives for grasping actions in order to gain insight into possible primitives used by the mirror system. In the present study, we investigated the potential of identifying such primitives using an action segmentation task. Specifically, we investigated whether or not segmentation was driven primarily by the kinematics of the action, as opposed to high-level top-down information about the action and the object used in the action. Participants in the experiment were shown 12 point-light movies of object-centered hand/arm actions that were either presented in their canonical orientation together with the object in question (top-down condition) or upside down (inverted) without information about the object (bottom-up condition). The results show that (1) despite impaired high-level action recognition for the inverted actions participants were able to reliably segment the actions according to lower-level kinematic variables, (2) segmentation behavior in both groups was significantly related to the kinematic variables of change in direction, velocity, and acceleration of the wrist (thumb and finger tips) for most of the included actions. This indicates that top-down activation of an action representation leads to similar segmentation behavior for hand/arm actions compared to bottom-up, or local, visual processing when performing a fairly unconstrained segmentation task. Motor primitives as parts of more complex actions may therefore be reliably derived through visual segmentation based on movement kinematics.

Expert Event Segmentation of Dance Is Genre-Specific and Primes Verbal Memory

“…Event borders in musical compositions can be detected in both trained and untrained musicians, and are differentiated by changes in tone, tempo, rhythm, pitch, and boundary silences [ 40 ]. Consistent with previously-identified movement event boundaries [ 1 , 41 , 42 , 43 ], changes in the direction of movement, pose, or position, relative location, speed, and acceleration were the most-commonly-identified event borders among all participants in the current study ( Figure 4 , Table 2 ). Observing both novel and learned action elicits activation from a distributed visuomotor network [ 21 , 24 , 44 , 45 , 46 ], including the frontal eye field [ 3 ], human MT+ complex [ 9 , 39 ], and posterior superior temporal sulcus [ 47 ], and is most active at event borders.…”

Complex Motor Learning and Police Training: Applied, Cognitive, and Clinical Perspectives

“…In order to do so, sensory-motor and memory regions of the brain are recruited to help break down continuous streams of motion (as well as music and language, see Zacks et al, 2009a; Francois and Schön, 2011; Lerner et al, 2011) into component “chunks” (Zacks and Sargent, 2010). Motor chunks begin and end with event borders that are typically marked by distinct kinematic movement parameters, including changes in position or location, speed, and direction of movement and also perceived changes in goals and intentions (Zacks et al, 2009b, 2010; Hemeren and Thill, 2011).…”

Parallels in Processing Boundary Cues in Speech and Action

“…For example, exaggeration of the prosodic boundary cues can bolster speech perception (e.g., better segmentation of strings of pseudowords spoken with infant-directed vs. adult-directed pitch contours; Thiessen et al, 2005), and likewise, exaggerated kinematic boundary cues (e.g., extending the pause) can improve memory for the individual actions constituting a sequence (Gold et al, 2017). Furthermore, “pure prosody” can signal a boundary, as evidenced by the findings of prosodic boundary processing in nonsense speech or even hummed speech (Pannekamp et al, 2005), and kinematic boundary cues seem to operate similarly, because acceleration and speed changes are interpreted as a marker of a boundary when observed movements are not discernible as actions (e.g., when hand movements are displayed as an inverted moving constellation of point-lights; Hemeren and Thill, 2010). Thus, the perceptual cues that mark boundaries in speech and in action sequences seem robust enough to signal the presence of a boundary in a perceived sequence independent of any contextual information.…”