This method is motivated by recent findings in two disparate fields. First, electrophysiological studies indicate that neuronal responses are more reliable (reproducible) under naturalistic stimulus conditions than under conventional laboratory conditions using artificial stimuli (Belitski et al., 2008; Mechler et al., 1998; Yao et al., 2007). Second, our human fMRI studies indicate that some natural stimuli evoke highly reliable, selective, and time-locked activity across a wide network of brain areas. The data are analyzed by comparing the neural (e.g., fMRI, ECOG) response timecourses across different subjects over the course of the natural stimulation (e.g. listening to a story or watching a movie). We called this correlation method inter-subject correlation (ISC; Figure 3A). The ISC analysis method differs from conventional fMRI data analysis methods in that it circumvents the need to specify a model for the neuronal processes in any given brain region during movie watching. Instead, the ISC method uses the subject’s brain responses to naturalistic stimuli as a model to predict brain responses within other subjects.
1. Hasson U, Nir Y, Levy I, Fuhrmann G, Malach R (2004) Intersubject synchronization of cortical activity during natural vision. Science 303:1634-1640. [PDF]
2. Mukamel R, Gelbard H, Arieli A, Hasson U, Fried I, Malach R (2005) Coupling between neuronal firing, field potentials, and FMRI in human auditory cortex. Science. [PDF]
3. Hasson U, Malach R, Heeger DJ (2010) Reliability of cortical activity during natural stimulation. Trends Cogn Sci 14:40-48. [PDF]
4. Ben-Yakov A, Honey CJ, Lerner Y, Hasson U (2012) Loss of reliable temporal structure in event-related averaging of naturalistic stimuli. NeuroImage 63:501-506. [PDF]
Inter-subject functional correlation