Tag: Brain Science

Non-human animal research has demonstrated the importance of a structure known as the hippocampus in processing a map of the animal’s environment stored in memory. Specific brain cells (neurons) in this structure, often referred to as place cells, fire when the animal is in a specific location. However, the contribution of these cells in human spatial memory has been uncertain.

A recent paper looked at the role of human hippocampal neurons in place learning using brain imaging techniques in patients with a rare condition known as Transient Global Amnesia.

Patients with Transient Global Amnesia have nearly total lack of memory of past events except for things of high importance like personal identity and are unable to form new memories. These episodes usually last about 6 to 10 hours and otherwise these patients are alert and seem normal. Relatively small areas of the part of the hippocampus thought to be important for place memory become temporarily disrupted (lesion) and can be detected with brain imaging techniques 1 to 3 days after the onset of a patient’s loss of memory.

These patients were tested in a place memory task while they experienced memory loss. Later the associated brain lesion was imaged. Patients with Transient Global Amnesia episode were significantly impaired in place memory tasks compared with normal subjects.

The paper, titled “Focal Lesions of Human Hippocampal CA1 Neurons in Transient Global Amnesia Impair Place Memory” and published June 11, 2010 in Science, demonstrates that at least some of the large amount of research done on the hippocampus’ role in place memory in non-human animals is applicable to humans.

A new review paper presents accumulated evidence that the brains of both mothers and fathers change in the service of parenting behavior. In addition, structural, electrophysiological and molecular changes occur in maternal and paternal brain regions not traditionally associated with parenting. Some of these brain areas are more widely known to be involved in cognition and mood regulation.

Maternal and paternal influences on neuroplasticity in the hippocampus and prefrontal cortex are highlighted in the review paper “Parenting and plasticity” published October 2010 in Trends in Neuroscience. The hippocampus and prefrontal cortex are well known and extensively studied for their roles in learning, memory, mood regulation, and cognition.

Some of the other brain regions known to be involved in maternal and paternal behavior include the olfactory bulb, medial preoptic area, lateral septum, bed nucleus of the stria terminalis, and the amygdala.

As a non-parent did you ever get annoyed by a crying baby? If you became a parent did you notice how your reaction to crying babies changed? Your brain changed! Data show that exposure to crying infants activates the amygdala and prefrontal cortex in fathers and mothers, but not in non-parents.

It’s been known for some time that mothers exhibit drastic alterations in hormones including decreased estrogen and increased oxytocin and prolactin. However, it has only recently been appreciated that fathers have similar, but not identical, alterations in these hormones including increased estrogen, oxytocin, prolactin and glucocorticoids. Oxytocin levels in human fathers are positively related to the amount of affection the father displays toward his infant. Paternal behavior is also related to reduced levels of testosterone.

These were just a couple of examples of how the brains of parents are clearly different from those of non-parents. The changes in maternal and, especially, paternal brains induced by the presence of offspring have only begun to be looked at. I encourage those interested in the subject to read this brief review paper.

Experiments described in a new paper used an impressive array of techniques to look at neuron activity in the whisker sensory cerebral cortex in awake mice performing an active tactile object localization task.

The authors of “Neural Activity in Barrel Cortex Underlying Vibrissa-Based Object Localization in Mice” published September 23, 2010 in Neuron asked “what information individual barrel cortex neurons might provide about object location.” A barrel in the cerebral cortex is the area receiving robust input from a single identified whisker (technically a vibrissa) on the rodent’s snout.

Using loose-seal cell-attached patch-clamping and two-photon imaging they found the following:

• Some neurons discriminated trial types nearly perfectly
• Over half of all neurons did not discriminate above chance levels
• Discrimination performance depended on the overall spike rate of the neuron and on cortical layer

The assumption they make is that discrimination is based on an absolute rate increase significantly above baseline.

The research team observed dramatic differences among cortical layers in overall spike rates and in the degree to which neurons of different layers carried information about the trial type. For instance, neurons in layers 2 and 3 showed sparse and low activity. Neurons in these layers sometimes showed a high degree of discrimination. Neurons in layer 6 showed low activity or ability to discriminate. In contrast Layer 4 and Layer 5 neurons showed high activity with relatively numerous neurons showing a high degree of discrimination.

The results of this study are intriguing. I particularly find the intracortical layer-by-layer differences fascinating. Nevertheless, I’m left with the sense that we remain a long way from actually understanding the original question “what information individual barrel cortex neurons might provide about object location.”

Other related blog posts:

Wiggling Whiskers for a Living?

Wiggling Whiskers: Directional Tuning

Whisker Related Brain Anatomy Data for Building Simulations