Author: Donald Doherty

  • Is the Conscious Decision an Illusion? Pursuing Goals Unconsciously

    Most of us consider that conscious will is the starting point of pursuing a goal. Recent discoveries challenge this view. The recent paper “The Unconscious Will: How the Pursuit of Goals Operates Outside of Conscious Awareness” published July 2, 2010 in Science reviews research that indicates that setting goals and then pursuing them may all happen without the involvement of conscious awareness.

    I recall my surprise when Benjamin Libet presented data that showed people beginning to act to fulfill a goal, in this case by moving their finger, before they made the conscious decision to act. The lecture was more than 25 years ago but I recall wondering if our conscious decisions were sometimes simply after-the-fact explanations for actions and goals we had already carried out without conscious awareness. Evidence accumulated since then suggests that this may be the case.

    The authors review recent research showing that social situations and other stimuli act to influence and control an individual’s pursuit of goals without the individual’s conscious awareness. But how can people determine whether it’s worth pursuing a given goal and invest effort in attaining it without the involvement of consciousness?

    Conscious awareness of rewards is not needed for the pursuit of goals to occur is the conclusion reached by the authors of this review. They point out that the brain processes and represents behaviorally relevant information in such a way that the pursuit of a goal can be controlled by the social situation without conscious awareness of the activation and operation of the goal.

  • Whole Brain Catalog: Visualizing Neural Network Activity

    The Whole Brain Catalog could become the gateway to the world’s brain related online data repositories (see my recent blog “Bio-Commons a Global Challenge“). If you’ve been following my posts on the Whole Brain Catalog you’ve seen how it enables you to visually dive into a mouse brain and explore data that exist on different scales such as brain cells (neurons) and protein molecules. Today you’ll look at a network of cells in the thalamus and cerebral cortex and then you’ll watch a simulation of the neural network’s activity.

    Note: If you haven’t installed the Whole Brain Catalog on your computer, please read my earlier post “Whole Brain Catalog: the Google Earth for the Brain.”

    A thalamocortical network is displayed in the Whole Brain Catalog.

    Go to the Data Type area to the left-bottom of the brain viewing area and click on the arrow to the left of “Cells.” This will open the list of cell types and groups of cells available to you. Find the “Thalamocortical Network” and check the box to the left of the label. Give Whole Brain Catalog time to download the data.

    Now you’d probably like to zoom in to take a look at the approximately 300 cells and thalamic inputs that you’ve placed into your Whole Brain Catalog mouse brain. Double clicking on “Thalamocortical Network” doesn’t do anything and there is no context menu available for this level. Go to a cell listed under “Thalamocortical Network” and double click or select “Zoom to” from the context menu. From there you may adjust your view to see the whole cluster of cells by using “Zoom out” or you may want to examine the cells close up.

    Tip: You can always zoom in and out using your plus (+) and minus (-) keys.

    The structure highlighted in yellow is a layer 2/3 pyramidal cell displayed within the context of a thalamocortical network in the Whole Brain Catalog.

    Part of the thalamus and cerebral cortex are represented in the “Thalamocortical Network.” In the thalamus, neurons in the thalamic reticular nucleus and inputs from a main relay nucleus (unspecified) are present. Excitatory cell types from 4 of the 6 layers found in the cerebral cortex are present including layer 4 Spiny Stellate cells, layer 2/3 pyramidal cells, layer 5 tufted pyramidal cells, and non-tufted pyramidal cells.

    Tip: Change the direction you’re looking by using your arrow keys.

    Now let’s view a simulation of the thalamocortical network. You need to download a data file to do this. Download the ThalamocorticalSimulationData.zip file from the Whole Brain Catalog website by clicking here. Place the downloaded file into a named folder you’ll remember (like WholeBrainCatalogData) and then unzip the file. When I unzipped the file a folder with a big long alpha-numeric label appeared, which is a good reason to open the zip file inside a well labeled folder.

    Open the context menu from any of the cells listed under “Thalamocortical Network.” Select the “Animate Network” menu item and an “Open” file dialog box will appear. Find the folder you placed the simulation data into and double click on it. Then double click on the data folder name inside to show a list of XML data files. Select any one of these data files and then click on the “Import File” button. Whole Brain Catalog will load all of the data files so please be patient.

    Note: Running the thalamocortical network takes significant computer power. You may find that the visualization runs slow or even blacks out if you don’t have a powerful enough computer.

    Note: To turn off the animation you select “Animate Network” from the context menu again. However, this didn’t work for me. The open files dialog box appeared again for me. I clicked the cancel button and the animation kept running.

    The features of the Whole Brain Catalog you used today are an impressive start. Nevertheless, there are many areas we should see improve in future releases. For instance, the location of the thalamocortical network within the brain makes no sense. The cells should be found in their appropriate anatomical locations. Also, showing animations of simulations using special data files is a first step towards the ideal of running and visualizing actual simulations based on neurobiological data within the context of the Whole Brain Catalog.

    Other related blog posts:

    Whole Brain Catalog: the Google Earth for the Brain

    Whole Brain Catalog: Brain Cells and Molecules

    Bio-Commons a Global Challenge

  • Where Did You Get the Impulse? Dopamine and Impulsivity

    The neurotransmitter dopamine has been implicated in impulsivity, reward, addiction, and motivation. In the recent paper “Dopaminergic Network Differences in Human Impulsivity” published July 30, 2010 in Science a research team asks if highly impulsive individuals have less midbrain dopamine autoreceptors than those with typical impulse personality traits.

    Autoreceptors play an important role in regulating the amount of neurotransmitter that stays in the synapse and for how long. Dopamine autoreceptors clear the synaptic cleft of dopamine neurotransmitter. The research team hypothesized that highly impulsive individuals have less midbrain autoreceptors available for the reuptake of the dopamine neurotransmitter. This would lead to more dopamine initiated spikes (action potentials) following exposure to novel, salient, or rewarding stimuli.

    To test their model, the team performed positron emission tomography scans on 32 physically and psychiatrically healthy volunteers using a dopamine receptor (D2 and D3) specific label. Each participant was evaluated for impulse personality traits using the Barratt Impulsiveness Scale. The relative amount of available D2 and D3 dopamine receptors in the striatum was assessed in each volunteer. They also looked at the amount of drug induced dopamine released into the striatum.

    They found that individuals displaying more impulsivity traits showed lower amounts of available dopamine autoreceptors in two areas of their brain that send dopamine terminals to the striatum ( specifically the ventral tegmental area and substantia nigra). They also found that individuals displaying more impulsivity traits showed higher amounts of drug induced release of dopamine into the striatum. They went one step further and asked each research subject if they wanted more of the drug that was used to induce the release of dopamine. Individuals with more impulsivity were more likely to want more of the drug.

    The results link less midbrain dopamine autoreceptors with more impulsivity and suggest a link between human impulsivity and vulnerability to drug abuse.