Psychology and neuroscience research typically adopt a reductionist, deductive approach to study particular cognitive and neurobiological processes. Empirical research in these fields has largely resorted to abstraction and simplification in order to achieve maximal control over as many variables as possible, while isolating or randomizing other intervening or potentially confounding factors. Despite their obvious advantages and past effectiveness, such experimental protocols lack the distinctive complexity of real life. The Hasson Lab attempts to develop complementary paradigms to study the neural activity that drives human behavior under natural and realistic conditions.
Below we summarize two current lines of research in the lab: Mapping of temporal receptive windows and Two-brain interactions.
Topographic mapping of a hierarchy of temporal receptive windows
In everyday life, memories of the past are constantly integrated with incoming information. Indeed, the contents of memory cannot be separated from ongoing stimulus processing (Fuster, 1997), as brain areas involved in primary processing also need to accumulate information across time (Lewis, 1979; Fuster, 1997; Kiebel et al., 2008; Buonomano and Maass, 2009; Albright, 2012). Consider, for example, how present and prior information converge when listening to speech: each phoneme achieves its meaning in the context of a word, each word in a sentence, and each sentence in a discourse. Thus, information gathered over milliseconds, seconds, and minutes all contributes to understanding. Comprehension of each word, sentence, or idea also relies on knowledge accumulated in the listener’s brain over many years. However, there is little research on the neural processes that allow the brain to gather information over time. The long-term goal of our laboratory is to understand how the brain uses information accumulated across multiple timescales, ranging from milliseconds to days, to make sense of moment-to-moment incoming information.
Our research shows that during continuous natural input, memory of past events influences online cortical activity. We call this type of influence “process memory,” defined as active traces of past information that are used by a neural circuit to process incoming information in the present moment (Hasson et al., TiCS 2015). Neural processes are defined as dynamic changes of the underlying brain states necessary for synthesizing information to guide behavior. Process memory has a clear hierarchical organization, in which its timescales gradually increase from early sensory areas that integrate over tens to hundreds of milliseconds to higher-order areas that integrate over many seconds to minutes.
We use functional magnetic resonance imaging (fMRI) and intracranial EEG (iEEG) recording to probe for TRWs in the brain. fMRI allows us to characterize the time scale of processing across the entire cortical surface, thus revealing large scale topographical principles. The high temporal resolution of the iEEG electrophysiological measurements allow us to validate predictions we make based on our BOLD data, to probe shorter time-scale receptive windows, and to link the properties of the proposed network of time scales to the broader neurophysiology literature.
In everyday life, we spend most of our time interacting with other individuals. The complexity of face-to-face interactions, however, has hindered scientists from directly probing the neural mechanisms underlying such interactive processes. Our new analytical methods remove such experimental boundaries and enable us to study the interaction between two brains in the course of natural verbal communication.
Uri Hasson, Professor,
Department of Psychology and the Neuroscience Institute, Princeton University.
"My research is part of a growing trend in neuroscience towards the study of brain responses to natural real life events. The Hasson Lab attempts to develop complementary paradigms to study the neural activity that drives human behavior under natural and realistic conditions.."
In one study, we used fMRI to record both the brain activity of a speaker telling an unrehearsed real-life story and the brain activity of a listener listening to a recording of the story. To make the study as ecological as possible, we instructed the speaker to speak as if telling the story to a friend. Next, we measured the brain activity of a listener hearing the recorded audio of the spoken story, thereby capturing the time-locked neural dynamics from both sides of the communication. Finally, we asked the listeners to complete a detailed questionnaire that assessed their level of comprehension.