Ole Jensen

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The role of occipital gamma activity in humans
from working memory to consolidation

• Ole Jensen
• F.C. Donders Centre for Cognitive Neuroimaging
• Nijmegen, The Netherlands

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The binding problem solvedby neuronal
synchronization
from Engel et al.
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Intracranial recordings revealing neuronal
synchronization
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fgamma 30-100 Hz
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Gamma synchronization in cats
fgamma 30-100 Hz
Gray et al. (1989) Nature
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Varela et al. (2001) Nat Rev Neuro
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Induced gamma activity inhumans reflecting
perception
Tallon-Baudry et al. (1997) J Neurosci
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Induced gamma activity inhumans reflecting
perception
Tallon-Baudry et al. (1997) J Neurosci
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Neurons synchronized at gamma provides a stronger
forward drive
Jensen et al. (2007) TINS
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Synchronization in the gammaband reflects visual
representations
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MEG
275 axial gradiometers
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WM maintenance
Baddeley and Hitch (1974)
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WM maintenance by gamma
Jensen et al. (2007) TINS
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Face identify vs. orientation
Jensen and Jokisch (2007) J Neurosci
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face orientation
. . .
dorsal
ventral
face identify
. . .
Jensen and Jokisch (2007) J Neurosci
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Gamma increases when engaging dorsal but not
ventral stream
Face identity
Face orientation
Jensen and Jokisch (2007) J Neurosci
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Gamma sources in primary visual cortex
Face
Orientation - Identity
Jensen and Jokisch (2007) J Neurosci
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Gamma increases when engaging dorsal but not
ventral stream
Face identity
Face orientation
RTidentity gt RTorientation !!!
Jensen and Jokisch (2007) J Neurosci
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Alpha increases when engaging ventral but not
dorsal stream
Face orientation
Face identity
Jensen and Jokisch (2007) J Neurosci
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Alpha sources in parieto-occipital cortex
ID face identity OR face orientation CO
control
Jensen and Jokisch (2007) J Neurosci
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dorsal
-
ventral

• Gamma reflects WM maintenance (not task demands!)
• Alpha reflects inhibition

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Encoding and recallfrom long-term memory
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Synaptic encoding of long-term memory
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Synaptic encoding of long-term memory
Encoding Synaptic modification by LTP is
enforced by multiple repetitions Recall How to
read-out of synaptically encoded
representations?
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Long-term memory study

• 240 pictures

240 old pictures 240 new pictures
Osipova et al. (2006) J Neurosci
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Long-term memory study

• 240 pictures

240 old pictures 240 new pictures
Osipova et al. (2006) J Neurosci
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Encoding gamma band power
Osipova et al. (2006) J Neurosci
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Encoding gamma band power
Osipova et al. (2006) J Neurosci
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Theta During Successful Encoding
Osipova, Takashima, Fernandez and Jensen (2006) J
Neuroscience
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Long-term memory study

• 240 pictures

240 old pictures 240 new pictures
Osipova et al. (2006) J Neurosci
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Retrieval gamma band power
Osipova et al. (2006) J Neurosci
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Retrieval gamma band power
Osipova et al. (2006) J Neurosci
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Encoding
Recognition
Occipital gamma provides a drive to association
areas facilitating synaptic encoding
Gamma reflects a pattern completion process in
visual areas (read-out from synaptic encoding)
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Changes in expression of long-termmemory
representations with stabilization
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Face - Location association
Nieuwenhuis et al. (2008) Neuroimage
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Training
Nieuwenhuis et al. (2008) Neuroimage
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Induced gamma during recall
Nieuwenhuis et al. (2008) Neuroimage
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Gamma reduced with LTM stabilization
Nieuwenhuis et al. (2008) Neuroimage
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Stabilization reflected in occipital areas
Nieuwenhuis et al. (2008) Neuroimage
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LTM recall labile versus stable representations
Labile (new)
Stable
See also fMRI study by Takashima et al. (2006)
Learning and memory.
Nieuwenhuis et al. (2008) Neuroimage
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Conclusion

• Human gamma activity can be detected and
  localized using MEG
• Sustained gamma during working memory maintenance
• Visual gamma reflect successful LTM encoding and
  recall
• Reliance on visual areas decreases with memory
  stabilization

Gamma activity reveals that early visual areas
are engaged in memory tasks (to a larger degree
than observed by fMRI)
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Dr. Daniel Jokisch Gamma and alpha activity in
working memory
Ingrid Nieuwenhuis Gamma and memory stabilization

• Dr. Atsuko Takashima
• Theta/gamma during declarative memory
• Gamma and memory stabilization

Dr. Dasha Osipova Theta/gamma during declarative
memory
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