An intracranial event-related potential study on transformational apparent motion. Does its neural processing differ from real motion?

Abstract

How the brain processes visual stimuli has been extensively studied using scalp surface electrodes and magnetic resonance imaging. Using these and other methods, complex gratings have been shown to activate the ventral visual stream, whereas moving stimuli preferentially activate the dorsal stream. In the current study, a first experiment assessed brain activations evoked by complex gratings using intracranial electroencephalography in 10 epileptic patients implanted with subdural electrodes. These stimuli of intermediate levels of complexity were presented in such a way that transformational apparent motion (TAM) was perceived. Responses from both the ventral and the dorsal pathways were obtained. The response characteristics of visual area 4 and the fusiform cortex were of similar amplitudes, suggesting that both ventral areas are recruited for the processing of complex gratings. On the other hand, TAM-induced responses of dorsal pathway areas were relatively noisier and of lower amplitudes, suggesting that TAM does not activate motion-specific structures to the same extent as does real motion. To test this hypothesis, we examined the activity evoked by TAM in comparison to the one produced by real motion in a patient implanted with the same subdural electrodes. Findings demonstrated that neural response to real motion was much stronger than that evoked by TAM, in both the primary visual cortex (V1) and other motion-sensitive areas within the dorsal pathway. These results support the conclusion that apparent motion, even if perceptually similar to real motion, is not processed in a similar manner.

Cross-Modal Re-Organization in Adults with Early Stage Hearing Loss

“…Higher-order visual cortical regions such as Brodmann areas 18 and 19, and the fusiform region, were also activated. These findings are consistent with previous studies, which used stimuli generally similar to ours in NH subjects [34], [47], [48], [49]. The P1 component showed similar cortical and cerebellar activation for both groups.…”

“…Participants were shown a high contrast sinusoidal concentric grating that morphs into a radially modulated grating or circle-star pattern [25], [33], [34] on a 26-inch flat-screen LCD television at a viewing distance of approximately 42 inches. The circle and star figures were presented 150 times.…”

The shape of motion perception: Global pooling of transformational apparent motion

“…Similarly, V3a also strongly responds to global motion stimuli (Braddick et al, 2000). Considered together with evidence that versions of TAM stimuli that do not control for motion energy seem to activate V5/MT (Tse, 2006; but see Bertrand et al, 2012), our results provide strong evidence that form information necessary for the TAM percept can enter the motion system by the level of V5/MT and/or V3a. This result is consistent with several different propositions about how form motion might reach V5/MT.…”

“…He showed that both form and motion processing areas (V2, V3, V3a, V5/MT, LOC) show greater activation for TAM compared to the static form stimuli. More recently, a study using intracranial electrode recordings that, unlike Tse (2006), carefully controlled for motion energy showed that TAM produces activation in LOC and V4 but only a weak response in V5/MT (Bertrand et al, 2012). On the other hand, if we do find that TAM globally integrates, then it would suggest the form information needed for TAM feeds into the motion system by at least this level.…”

Developmental and cross-modal plasticity in deafness: Evidence from the P1 and N1 event related potentials in cochlear implanted children

“…3A we show cortical activation elicited by visual stimuli in a normal hearing (NH) child (left panel), a high-performing cochlear implanted child (middle panel), and an average-performing cochlear implanted child (right panel). The visual stimuli used have been shown to activate higher-order visual cortices, including both dorsal and ventral streams due to the percept of apparent motion and shape change (Bertrand et al, 2012; Campbell & Sharma, 2014; Doucet et al, 2006; Wilkinson et al, 2000). As can be seen for the P2 cortical visual evoked potential (VEP) component, the NH child and the high-performing cochlear implanted child (96% speech perception score) show expected occipital activation in response to visual stimulation, including higher-order visual cortex (middle occipital gyrus, fusiform gyrus, and lingual gyrus).…”