User:Ionela Bara/sandbox

Implied motion

Implied motion is a perceptual phenomenon defined as the visual system’s ability to detect movement in a static image, such as a picture capturing a running athlete. The perception of motion in static photos that contain no physical motion is accomplished by several motion cues, such as the speed lines, broken symmetry or stroboscopic effects. They all have been used by the image-makers for centuries, from cartoonists to painters, in order to convey a sense of dynamism in a stationary image. One of the most used motion cues, especially in cartoons, is the speed lines or motion lines and refer to parallel lines drawn onto direction of the movement to suggest the speed of an object.

Neuroanatomy

The research studies conducted into the neuroanatomy of implied motion, aimed to identify distinct brain regions or brain networks responsible for detection and processing of implied motion cues. It was the rapid advancement of neuroimaging technologies that made possible the investigation of implied motion neuroanatomy. Powerful neuroimaging methods, such as single-cell recording, functional magnetic resonance imaging (fMRI), Electroencephalography (EEG), or transcranial magnetic stimulation (TMS) largely contributed to our understanding of the structure and function of brain regions involved in implied motion.

Neuroimaging methods

Animal studies

The studies conducted on primate brain mainly investigated whether the brain areas known to be involved in biological motion processing would be also activated by implied motion. For example, a research study used a single and multi-unit recording method to test the activity of V5 neurons of macaque monkeys. The researchers recorded the signal from MT (medial temporal)/MST(medial superior temporal) areas, while presenting to the animal moving stimuli and pictures with implied motion. They found stronger activation in MT/MST for both situations: real and implied motion, suggesting that MT/MST areas are responsible with processing biological motion and implied motion too.

Human studies

One of the early research studies using a fMRI method examined whether the visual area MT/MST would show higher response to implied motion compared with no implied motion. The researchers defined MT/MST brain area as a functional region of interest (fROI) which they tested it by showing to participants pictures with implied motion and pictures with no implied motion. They found stronger activation of MT/MST for pictures with implied motion compared with pictures with no implied motion, demonstrating that the cortical region involved in the analysis of physical motion is also involved in implied motion processing. This idea that MT/MST brain region is engaged in both physical and implied motion processing appears to be a robust finding, as other research studies firmly support this hypothesis as well.

As an example, a fMRI study found that when people viewed static images depicting motion the most powerful cortical activation was produced in the MT/MST brain areas, providing therefore support for the hypothesis that physical motion and implied motion is processed by identical brain regions. Additionally, the authors found that superior temporal sulcus (STS) was also involved in implied motion, suggesting that implied motion processing relies on higher-level processing as well. It is worth mentioning that alongside with biological motion, STS has been associated with one’s knowledge of social norms in social interactions, and with making judgments about other states of mind. Similarly, another study showed that observation of static photos depicting humans in different poses and actions determined a clear activation of MT/MST, but at the same time stimulated the extrastriate body area (EBA), suggesting that an interaction between different cortical areas in implied motion processing may depend on the nature of stimuli (e.g., faces, bodies). Indeed, this interplay between low-level processing (MT/MST) and high-level processing (STS, EBA) in implied motion has been demonstrated by other neuroimaging research studies as well. For example, employing an Electroencephalography (EEG) technique, a study indicated that when people viewed pictures conveying a sense of movement, the brain responses occurred 100msec later compared with real motion, suggesting that implied motion processing may need more time to integrate the feedback from higher level functions. Also, using a Transcranial magnetic stimulation (TMS) method, a study found that stimulation over MT/MST brain areas at 0, 50, 100, and 150 msec to stimulus presentation disrupted real motion processing but not implied motion processing. The authors interpreted this null effect on implied motion task as an indication that the activation of MT/MST may occur after 150msec, as implied motion processing may need an input from higher level cortical functions.

Altogether, these neuroimaging studies demonstrated that processing implied motion from static images involves MT/MST areas, but at the same time higher cognitive functions, such as STS, EBA are engaged as well, emphasising a role of top-down processes in implied motion.

Implications to Neuroaesthetics

Neuroaesthetics is one particular field within the cognitive neuroscience domain that manifested increased interest toward the investigation of implied motion, especially in relation with pictorial art. It is important to mention that for pictorial art the representation of movement in still images has been a challenge for centuries, long before the invention of photography. To date, there is some neuroimaging evidence to illustrate that people tend to evaluate as more aesthetically pleasing a painting that contains implied motion cues than a painting that convey no sense of dynamism.

Using a fMRI method, a research study found that participants associated the aesthetic experience with viewing paintings that contained implied motion and which strongly activated the cortical areas MT/MST. In addition to visual processing, the aesthetically pleasing paintings engaged strong signal from anterior prefrontal cortex as well, suggesting that implied motion processing needs input form both lower and higher cognitive functions, and that conveying dynamism is a quality associated with aesthetic experience. Similarly, this interplay between implied motion and higher cognitive functions in aesthetic experience has been demonstrated by a different study, who found that nature scenes with dynamic content activated brain regions, such as MT/MST, EBA, STS and at the same time they were associated with higher aesthetic ratings compared with nature scenes with no implied motion. Furthermore, a study using repetitive transcranial magnetic stimulation (rTMS) found that when participants viewed paintings with implied motion, the motor-evoked potentials increased in size, modulating the plasticity and connectivity in the dorsal premotor cortex, suggesting a potential role of implied motion in brain plasticity

Altogether, these studies conducted within the field of Neuroaesthetics supported the main cognitive neuroscience research hypothesis that implied motion processing is engaging similar cortical brain regions as biological motion (MT/MST). At the same time, the studies carried within Neuroaesthetics are in consensus with the idea that implied motion processing is a result of an interaction between low and high cognitive functions. Also, recent research studies introduced a new hypothesis according to which an image depicting movement may be more aesthetically pleasing than an image with no depicted motion.