Curr Biol. 2007 Feb 7;
Haynes JD, Sakai K, Rees G, ...
When humans are engaged in goal-related processing, activity in prefrontal cortex is increased . However, it has remained unclear whether this prefrontal activity encodes a subject's current intention . Instead, increased levels of activity could reflect preparation of motor responses , holding in mind a set of potential choices , tracking the memory of previous responses , or general processes related to establishing a new task set. Here we study subjects who freely decided which of two tasks to perform and covertly held onto an intention during a variable delay. Only after this delay did they perform the chosen task and indicate which task they had prepared. We demonstrate that during the delay, it is possible to decode from activity in medial and lateral regions of prefrontal cortex which of two tasks the subjects were covertly intending to perform. This suggests that covert goals can be represented by distributed patterns of activity in the prefrontal cortex, thereby providing a potential neural substrate for prospective memory . During task execution, most information could be decoded from a more posterior region of prefrontal cortex, suggesting that different brain regions encode goals during task preparation and task execution. Decoding of intentions was most robust from the medial prefrontal cortex, which is consistent with a specific role of this region when subjects reflect on their own mental states.
Science, Vol 308, Issue 5722, 644-645 , 29 April 2005 doi:10.1126/science.1112174
Kiyoshi Nakahara and Yasushi Miyashita
A class of neurons in the brain called "mirror neurons" may be crucial for understanding motor actions. Mirror neurons are activated not only during the execution of a particular action, but also during observation of that action carried out by someone else. In their Perspective, Nakahara and Miyashita discuss a new study in monkeys (Fogassi et al.) suggesting that mirror neurons also are able to encode the intention of a particular action as well as the action itself and observation of the action.
Nature Neuroscience January 2004 Volume 7 Number 1 pp 80 - 84 doi:10.1038/nn1160
Angela Sirigu1, Elena Daprati1, 2, Sophie Ciancia1, Pascal Giraux1, Norbert Nighoghossian3, Andres Posada1 & Patrick Haggard4
A central question in the study of human behavior is the origin of willed action. EEG recordings of surface brain activity from human subjects performing a self-initiated movement show that the subjective experience of wanting to move follows, rather than precedes, the 'readiness potential'—an electrophysiological mark of motor preparation. This raises the issue of how conscious experience of willed action is generated. Here we show that patients with parietal lesions can report when they started moving, but not when they first became aware of their intention to move. This stands in contrast with the performance of cerebellar patients who behaved as normal subjects. We thus propose that when a movement is planned, activity in the parietal cortex, as part of a cortico-cortical sensorimotor processing loop, generates a predictive internal model of the upcoming movement. This model might form the neural correlate of motor awareness.
Science, Vol 305, Issue 5681, 258-262 , 9 July 2004 doi:10.1126/science.1097938
S. Musallam, B. D. Corneil, B. Greger, H. Scherberger, R. A. Andersen
Recent development of neural prosthetics for assisting paralyzed patients has focused on decoding intended hand trajectories from motor cortical neurons and using this signal to control external devices. In this study, higher level signals related to the goals of movements were decoded from three monkeys and used to position cursors on a computer screen without the animals emitting any behavior. Their performance in this task improved over a period of weeks. Expected value signals related to fluid preference, the expected magnitude, or probability of reward were decoded simultaneously with the intended goal. For neural prosthetic applications, the goal signals can be used to operate computers, robots, and vehicles, whereas the expected value signals can be used to continuously monitor a paralyzed patient's preferences and motivation.
Science Volume 303, Number 5661, Issue of 20 Feb 2004, pp. 1208-1210. doi:10.1126/science.1090973
Hakwan C. Lau, Robert D. Rogers, Patrick Haggard, Richard E. Passingham1
Intention is central to the concept of voluntary action. Using functional magnetic resonance imaging, we compared conditions in which participants made self-paced actions and attended either to their intention to move or to the actual movement. When they attended to their intention rather than their movement, there was an enhancement of activity in the pre-supplementary motor area (pre-SMA). We also found activations in the right dorsal prefrontal cortexand left intraparietal cortex. Prefrontal activity, but not parietal activity, was more strongly coupled with activity in the pre-SMA. We conclude that activity in the pre-SMA reflects the representation of intention.
Kohler E., Keysers C., Umilta M.A., Fogassi L., Gallese V., Rizzolatti G. Hearing sounds, understanding actions: action representation in mirror neurons. Science, 297: 846-848, 2002. doi:10.1126/science.1070311
Many object-related actions can be recognized by their sound. We found neurons in monkey premotor cortex that discharge when the animal performs a specific action and when it hears the related sound. Most of the neurons also discharge when the monkey observes the same action. These audiovisual mirror neurons code actions independently of whether these actions are performed, heard,or seen. This discovery in the monkey homolog of Broca’s area might shed light on the origin of language: audiovisual mirror neurons code abstract contents - the meaning of actions - and have the auditory access typical of human language to these contents.