Decreased demands on cognitive control reveal the neural processing benefits of forgetting

Nature Neuroscience - 10, 908 - 914 (2007) doi:10.1038/nn1918

Brice A Kuhl et el

  • Remembering often requires the selection of goal-relevant memories in the face of competition from irrelevant memories. Greater forgetting of competing memories was associated with a greater decline in demands on prefrontal cortex during target remembering. These findings indicate that, although forgetting can be frustrating, memory might be adaptive because forgetting confers neural processing benefits.

new neurons in memory networks

Nature Neuroscience - 10, 273 - 275 (2007) doi:10.1038/nn0307-273

Josef Bischofberger

In the adult hippocampus, a brain region that is important for memory, new neurons are generated continuously. A study now shows that these newly generated neurons are preferentially activated during learning and recall of new memories.

Memory consolidation during sleep

Nishida, M. & Walker, M. P. (2007). Daytime naps, motor memory consolidation and regionally specific sleep spindles. PLoS One 2: e341. doi:10.1371/journal.pone.0000341

Memories are consolidated during sleep. Motor learning and declarative memory, for example - is enhanced as we sleep during the night. Enhanced memory consolidation takes place during the non-rapid eye movement (NREM) stage of sleep. This study shows that afternoon naps have the same effect on memory formation.

Nature Reviews Neuroscience 8, 86-87 (February 2007) doi:10.1038/nrn2084

During the first phase of sleep our brain is occupied with our last awake experiences. Does this 'revisiting' of events consolidate these experiences as memories? In Nature Neuroscience, Ji and Wilson have now shown that the firing patterns during awake experiences are replayed in the hippocampus and cortex in a coordinated manner during slow wave sleep (SWS), suggesting a mechanism for memory consolidation.

Neuroanatomy: Brain asymmetry and long-term memory

Nature 427, 605 - 606 (12 February 2004); doi:10.1038/427605a


The asymmetrical positioning of neural structures on the left or right side of the brain in vertebrates and in invertebrates may be correlated with brain laterality, which is associated with cognitive skills. But until now this has not been illustrated experimentally. Here we describe an asymmetrically positioned brain structure in the fruitfly Drosophila and find that the small proportion of wild-type flies that have symmetrical brains with two such structures lack a normal long-term memory, although their short-term memory is intact. Our results indicate that brain asymmetry may be required for generating or retrieving long-term memory.

Memory suppression

Science Volume 303, Number 5655, Issue of 9 Jan 2004, pp. 232-235.

Neural Systems Underlying the Suppression of Unwanted Memories Michael C. Anderson,1* Kevin N. Ochsner,2 Brice Kuhl,1 Jeffrey Cooper,2 Elaine Robertson,2 Susan W. Gabrieli,2 Gary H. Glover,3 John D. E. Gabrieli2

Over a century ago, Freud proposed that unwanted memories can be excluded from awareness, a process called repression. It is unknown, however, how repression occurs in the brain. We used functional magnetic resonance imaging to identify the neural systems involved in keeping unwanted memories out of awareness. Controlling unwanted memories was associated with increased dorsolateral prefrontal activation, reduced hippocampal activation, and impaired retention of those memories. Both prefrontal cortical and right hippocampal activations predicted the magnitude of forgetting. These results confirm the existence of an active forgetting process and establish a neurobiological model for guiding inquiry into motivated forgetting.

Prions in memory?

Long-Term Memory: A Positive Role for a Prion? Ingrid Wickelgren

Prions are famous evildoers. These proteins, which are thought to be misfolded versions of normal ones, cause deadly neurodegenerative diseases, including "mad cow disease," in mammals. In yeast, however, prions are largely benign, if nonfunctional (Science, 2 August 2002, p. 758). Now, a team led by neuroscientist Eric Kandel and postdoc Kausik Si at Columbia University College of Physicians and Surgeons in New York City may have discovered the first positive function for a prionlike protein: the formation of long-term memories.

In two papers in the 26 December issue of Cell, the Columbia researchers, along with Susan Lindquist of the Whitehead Institute in Cambridge, Massachusetts, show that cytoplasmic polyadenylation element binding protein (CPEB) is required for cementing cellular long-term memories in neurons of the sea slug Aplysia. In yeast, the papers show, this same protein acts like a prion, and its prion form appears to be the one active in memory formation.

The work has led to the radically new notion--which is far from proven--that prionlike changes in protein shape may be a key molecular event in the formation of stable memories. Neuroscientist Solomon Snyder of Johns Hopkins University in Baltimore, Maryland, calls the work "a breath of fresh air." He adds: "It's the first truly novel concept about a molecular mechanism for learning and memory in perhaps 30 years." If the work holds up, it will broaden scientists' views of prions, hinting that they could play roles in development and other body functions that require long-lasting proteins, a hallmark of prions.