Forget about using only half a brain

I do find the idea of left-brained and right-brained types to be unconvincing. When I first encountered the idea I was intrigued and tested the theory out in my family, friends and myself. What I found in my tiny sample was a lack of a pattern. I found people who were very logical and also very creative – which came more to the fore depended on what they were doing. There were people who showed the one strength more than the other, but still seemed to have some of the other when it was really needed. And of course, there were a few that were both fairly illogical and fairly uncreative – one might say they were not that bright. To me, the idea that there are two kinds of people is in the eye of the beholder. Scientists tend to be creative even though they must be logical; novelists tend to be logical even though they must be creative. Why are these cast as opposites?

Think about it, why would we have evolved, not an optimal archetype, but instead, a pair of sub-optimal archetypes. Why would we not be able to think logically when that was what would solve a problem, think creatively when that was what would work, or think both ways if that was required. The two hemispheres having different functions appears to be an ancient structural feature – maybe to do with a division of labour between immediate tasks and general lookout for danger. But the idea that the hemispheres can not work together at the same time on different cognitive tasks is not very believable.

The notion that there are “two types of people in the world, those that x and those that y”, seems to be an easy trap to fall into. So get your antenna tuned to notice when the world is being divided into opposites, types, domains, dimensions and the like, and be extra skeptical. The division may work well or it may be just pretty and simplistic.

Recent research (see citation below) has failed to find left-brained and right-brained people in a sample of more than a 1000 scans of neural connections in a resting state. There are networks that are restricted to one hemisphere (more or less), but the strength of these connections does not show the x-brain effect.

we demonstrate that left- and right-lateralized networks are homogeneously stronger among a constellation of hubs in the left and right hemispheres, but that such connections do not result in a subject-specific global brain lateralization difference that favors one network over the other (i.e. left-brained or right-brained). Rather, lateralized brain networks appear to show local correlation across subjects with only weak changes from childhood into early adulthood and very small if any differences with gender.”

Here is the abstract:

Lateralized brain regions subserve functions such as language and visuospatial processing. It has been conjectured that individuals may be left-brain dominant or right-brain dominant based on personality and cognitive style, but neuroimaging data has not provided clear evidence whether such phenotypic differences in the strength of left-dominant or right-dominant networks exist. We evaluated whether strongly lateralized connections covaried within the same individuals. Data were analyzed from publicly available resting state scans for 1011 individuals between the ages of 7 and 29. For each subject, functional lateralization was measured for each pair of 7266 regions covering the gray matter at 5-mm resolution as a difference in correlation before and after inverting images across the midsagittal plane. The difference in gray matter density between homotopic coordinates was used as a regressor to reduce the effect of structural asymmetries on functional lateralization. Nine left- and 11 right-lateralized hubs were identified as peaks in the degree map from the graph of significantly lateralized connections. The left-lateralized hubs included regions from the default mode network (medial prefrontal cortex, posterior cingulate cortex, and temporoparietal junction) and language regions (e.g., Broca Area and Wernicke Area), whereas the right-lateralized hubs included regions from the attention control network (e.g., lateral intraparietal sulcus, anterior insula, area MT, and frontal eye fields). Left- and right-lateralized hubs formed two separable networks of mutually lateralized regions. Connections involving only left- or only right-lateralized hubs showed positive correlation across subjects, but only for connections sharing a node. Lateralization of brain connections appears to be a local rather than global property of brain networks, and our data are not consistent with a whole-brain phenotype of greater “left-brained” or greater “right-brained” network strength across individuals. Small increases in lateralization with age were seen, but no differences in gender were observed.

I assume that the left or right brain description of individuals will die a very slow death and years from now people will be using the labels – too bad, that’s life.

ResearchBlogging.org

Nielsen JA, Zielinski BA, Ferguson MA, Lainhart JE, & Aderson JS (2013). An Evaluation of the Left-Brain vs. Right-Brain Hypothesis with Resting State Functional Connectivity Magnetic Resonance Imaging PLoS ONE, 8 (8) : 10.1371/journal.pone.0071275

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Flexibility

ScienceDaily has an item (here) about a paper: Cole, Reynolds, Power, Repovs, Anticevic, Braver; “Multi-task connectivity reveals flexible hubs for adaptive task control” inNature Neuroscience 2013; dealing with a theory about the brain’s flexibility.

 

 

The basic idea is that the cortex has 300 or so areas with special cognitive abilities; these areas are connected through hub neurons; and the hubs form a dozen or so large networks by mutual interconnections, such as the visual, motor, or attention networks. For any particular cognitive task, certain areas will have abilities that are needed for the task and hubs must be connected to allow these areas to work together. These areas may be spread across several networks. The ability to flexibly connect hubs allows us to do novel tasks, switch between tasks quickly, re-use techniques for a different task and learn from verbal/visual instruction. This research looks at the lateral prefrontal cortex and the posterior parietal cortex as a network that can flexibly connect areas of the brain to different cognitive tasks. (In other publications they also mention the basal ganglia and thalamus being involved in the mechanism of these flexible connections.)

 

 

Acting as a central switching station for cognitive processing, this fronto-parietal brain network funnels incoming task instructions to those brain regions most adept at handling the cognitive task at hand, coordinating the transfer of information among processing brain regions to facilitate the rapid learning of new skills, the study finds.”

 

This study proposes and provides strong evidence for a “flexible hub” theory of brain function in which the fronto-parietal network is composed of flexible hubs that help to organize and coordinate processing among the other specialized networks…This study provide strong support for the flexible hub theory in two key areas…First, the study yielded new evidence that when novel tasks are processed flexible hubs within the fronto-parietal network make multiple, rapidly shifting connections with specialized processing areas scattered throughout the brain…Second, by closely analyzing activity patterns as the flexible hubs connect with various brain regions during the processing of specific tasks, researchers determined that these connection patterns include telltale characteristics that can be decoded and used to identify which specific task is being implemented by the brain.”

 

The flexible hub theory suggests this is possible because flexible hubs build up a repertoire of task component connectivity patterns that are highly practiced and can be reused in novel combinations in situations requiring high adaptivity.”

 

Flexible hubs differ from other hubs in that they are connected to many hubs outside their network (rather than having most of their connections within their network) and the strength of these connections can be varied quickly.

 

Another instance of consciousness

ScienceDaily (here) and (in more detail) a blog by Ed Yong (here) discuss a paper by Jimo Borjigin and others; “Surge of Neurophysiological Coherence and Connectivity in the Dying Brain” in PNAS. The paper is about near-death experiences.

 

 

Here is the abstract:

 

The brain is assumed to be hypoactive during cardiac arrest. However, the neurophysiological state of the brain immediately following cardiac arrest has not been systematically investigated. In this study, we performed continuous electroencephalography in rats undergoing experimental cardiac arrest and analyzed changes in power density, coherence, directed connectivity, and cross-frequency coupling. We identified a transient surge of synchronous gamma oscillations that occurred within the first 30 s after cardiac arrest and preceded isoelectric electroencephalogram. Gamma oscillations during cardiac arrest were global and highly coherent; moreover, this frequency band exhibited a striking increase in anterior–posterior-directed connectivity and tight phase-coupling to both theta and alpha waves. High-frequency neurophysiological activity in the near-death state exceeded levels found during the conscious waking state. These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.

 

 

The neural correlates of consciousness are synchronized gamma waves connecting distant parts across the cortex together and involving a loop with the thalamus. What they seem to have found is a short period strong synchronized gamma waves, indicating consciousness during the first half second of cardiac arrest, with strong coupling to theta and alpha waves – a super level of consciousness fitting with the very vivid memories of near-death experiences in humans.

 

 

There are still questions of what the mechanism is for this burst of conscious activity. Is something being released by the brain cells as they die that enhances activity for a short period? Is some brake on extreme activity released? Is the brain actually (unlikely as it may be) trying to think a way out of death? Is there an attempt to re-establish a balance that is disappearing?

 

 

Of course, some people have found it hard to accept that rats might have near-death experiences, or that near-death experiences could be explained as brain activity with no super-natural cause. But, that is to be expected. Near-death experiences were one of the only refuges left for the idea of a form of consciousness that could be independent of the body.

 

 

 

Is consciousness needed for inhibition of action?

Starting with Libet’s work in 1985, a body of evidence has been built up suggesting that actions can be initiated unconsciously and unintentionally. This evidence questions the idea of complete conscious control over behavior, and the philosophical idea of free will.

The idea of ‘free won’t', however remained. According to some influential theories, unconscious behaviours are the inflexible reproduction of well-learned associations. To understand consciousness we need to discover what processes need consciousness and which don’t. Is consciousness required to inhibit actions?

Experiments seemed to show that subliminal signals could inhibit action. Then the theories on unconscious engagement of inhibition suggests that (a) consciousness is in fact required for inhibitory control in that the stimuli were first consciously associated with inhibition before being used subliminally and (b) willful conscious intent is also required to form a goal or desire to modulate inhibition. Also it was thought that unconscious inhibition might be the result of modulation of motor control processes rather than normal inhibitory control processes.

A recent paper by Hepler and Albarracin (see citation) tackle this question. They found a method of using word primes that suggested action or inaction (as opposed to a specific action) and used the P3 wave strength to gauge the inhibitory processes. The experiments side-step the three possibilities of the arguments against unconscious inhibition of actions.

“This research represents a critical finding in the scientific study of consciousness because it demonstrates that inhibitory self-control mechanisms can operate unconsciously and unintentionally, without prior conscious input – that is, inhibition processes can be engaged by motivationally relevant stimuli that have never been consciously or unconsciously paired with specific, task-relevant responses. Although previous work has demonstrated similar effects on behavior, behavioral inhibition can occur as the result of multiple cognitive processes other than the engagement of inhibitory control mechanisms. Thus, the present research is the first to demonstrate that inhibitory control mechanisms can be modulated completely outside of conscious control. ”

This should be the end of the free-won’t model.
ResearchBlogging.org

Justin Hepler, & Dolores Albarracin (2013). Complete unconscious control: Using (in)action primes to demonstrate completely unconscious activation of inhibitory control mechanisms Cognition, 128 (3) : 10.1016/j.cognition.2013.04.012

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Over-thinking

ScienceDaily (here) has an item: Lee, Blumenfeld, D’Esposito; Disruption of Dorsolateral But Not Ventrolateral Prefrontal Cortex Improves Unconscious Perceptual Memories; inJournal of Neuroscience, 2013. It looks at the mechanism of over-thinking.

 

 

There are two types of memory (at least): explicit, conscious memory, also called declarative; and, implicit, not conscious memory, also called procedural. It has been noted for some time that preformance in sports, music and the like suffers when the performer thinks consciously too much. Procedural memory works best if the action is just done without trying to consciously control the action.

 

 

Two previous brain studies have shown that taxing explicit memory resources improved recognition memory without awareness. The results suggest that implicit perceptual memory can aid performance on recognition tests. So Lee and his colleagues decided to test whether the effects of the attentional control processes associated with explicit memory could directly interfere with implicit memory.”

 

 

Lee disrupted activity in two parts of the prefrontal cortex to see which affected recognition. Disrupting the dorsolateral PFC improved memory. This pointed to explicit memory processing taking control of visual information processing and so interfering with implicit memory processes using the same visual information.

 

 

Here is the abstract:

 

Attentive encoding often leads to more accurate responses in recognition memory tests. However, previous studies have described conditions under which taxing explicit memory resources by attentional distraction improved perceptual recognition memory without awareness. These findings lead to the hypothesis that explicit memory processes mediated by the prefrontal cortex (PFC) can interfere with memory processes necessary for implicit recognition memory. The present study directly tested this hypothesis by applying transcranial magnetic stimulation separately over either dorsolateral (DLPFC) or ventrolateral PFC (VLPFC) in humans before performance of a visual memory task. Disruption of DLPFC function led to improvement in recognition accuracy only in responses in which the participant’s awareness of memory retrieval was absent. However, disruption of VLPFC function led to subtle shifts in recollection and familiarity accuracy. We conclude that explicit memory processes mediated by the DLPFC can indirectly interfere with implicit recognition memory.

 

 

Involuntary autobiographical memories

I have just read a short article by Bradley, Moulin and Kvavilashvili in the March 2013 edition of The Psychologist, the BPS offical publication called Involuntary autobiographical memories.

 

 

Involuntary autobiographical memories (IAMs), pop into our minds without any deliberate attempt at retrieving them. They have been proposed as the result of ecphory, an automatic memory process where events, words or objects in the environment match stored information and bring a related memory into consciousness without any ‘request’ for its retrieval. Although they are very common and normal, they can be troublesome in PTSD flashbacks, epilepsy and under some drugs.

 

 

The IAMs that people notice and make note of seem to occur when they are not concentrating on a task but instead doing something like walking or eating. But with other methodology they can occur more often. One method is to record subjects as they generate continuous free word associations for half a minute and then play them the tape and have them report any autobiographical memories that had come to mind during the chain of associations. About 90% had IAMs. So they are probably much more common than we notice.

 

 

IAMs are more likely to be of a specific event, and come to mind significantly faster than voluntary autobiographical memories. They are also more likely to result in bodily reactions and impact on current mood than voluntary memories. However, no differences were observed in terms of perspective experienced in memory (field vs. observer) and the accuracy (measured by participants’ own confidence ratings) of recorded memories.”

 

According to Conway and Pleydell- Pearce’s influential model of autobiographical memory, during involuntary recall ‘ecphoric’ cues can bypass the usual top-down strategic retrieval pathway, involving activation of the left frontal lobe, resulting in a rapid formation of memory.”

 

When Penfield stimulated the temporal lobe – “The resulting phenomena included sights, sounds and emotions of past events, which the patients recognised spontaneously as personal experiences, and noted that their ‘vividness or wealth of detail and the sense of immediacy that goes with them serves to set them apart from the ordinary process of recollection’ .”

 

Hall carried out a PET study in healthy controls, using emotionally charged pictorial cues, and found that involuntary memory retrieval by-passed the initial search process, mediated by the prefrontal cortex, which occurs in conscious voluntary retrieval. This concurs with Conway … that involuntary retrieval can bypass the pathway involving activation of the left prefrontal lobe. ”

 

Because of the automatic nature of retrieval, involuntary memories may not require any working memory input. ”

 

 

The authors of this article and their sources appear to treat IAMs as common but not that common and fairly vivid. These are the ones people are aware of, anyway. But I am inclined to think that this automatic presentation of memories is going on much of the time. And much of it would not be surprising or noteworthy . Computers have procedures to guess what the CPU is going to want fetched next on the basis of what the last few fetches were. Many systems (car suspensions for example on expensive cars) have ways to look ahead and prepare for future demands. This is a common method of increasing efficiency. Why would our memories not have an automatic ‘lookahead’? Clues that we encounter should give us access to past experiences that may be helpful in the near future, and should do it immediately and without us realizing we needed that help. Those that are exceptional memories for one reason or another would become prominent in the stream of consciousness and if it is not obvious that the memory was prompted by this or that item in consciousness then it would appear to ‘pop’ in.

 

More than thalamus and cortex

For some time I have been trying to understand the relationship between the thalamus and the cortex in consciousness. I have been ignoring the basal ganglia. That is probably a mistake, for although the basal ganglia do not seem to be at the heart of consciousness (as the thalamus and cortex are), they are probably involved to some extent. They are certainly important to movement, decisions, and emotions at least.

basalganglia

I have taken some illustrations from Scholarpedia to show the complexity and the interconnectedness of the feedback loops through the basal ganglia. In all of these diagrams the neurotransmitters are coded: dopamine is green, GABA (inhibitory) is blue and glutamate (excitatory) is red. Output can roughly be thought of as the balance between direct striatonigral inhibitory connections that promote behaviour (the direct pathway), and the indirect pathway via relays in the external globus pallidus (GPe) and subthalamic nucleus (STN) which suppresses behaviour. The balance between these two projections was thought to be regulated by afferent dopaminergic signals from substantia nigra pars compacta (SNc) acting on differentially distributed D1 and D2 dopamine receptors.

Functional territories represented at the level of cerebral cortex are maintained thoughout the basal ganglia nuclei and the thalamic relays. Note, however, for each loop, the relay points in the cortex, basal ganglia, and thalamus, offer opportunities for activity inside the loop to be modified/modulated by signals from outside the loop.

loops

These loops are in addition to the thalamocortical loops that are necessary for consciousness.

ResearchBlogging.org

Peter Redgrave (2011). Basal Ganglia scholarpedia, 2 (6) DOI: 10.4249/scholarpedia.1825

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Emergent properties

Emergent properties is a phrase that I find difficult to pin down. This is not an unusual thing with words; many words are ambiguous in many useful ways. Probably all words have some level of ambiguity. However when I encounter emergent properties I get a feeling of something that can plainly be said is being avoided. It seems a slippery phrase meant to hide meaning. Of course, this is my reaction and not necessarily the author’s intent. The author may have a particular ambiguity in mind and feels he is being open about it. Unfortunately, my reaction is to immediately distrust the author and to look for what they are hiding.

 

Emergent properties may be as mundane as ‘the whole is greater than the sum of its parts’, which is true of many (maybe most) things and hardly worth mentioning. It may be being used to say, ‘this is understandable at a level higher than elementary physics, say thermodynamics or biology or meteorology’. Again this is a mundane observation as everything except elementary physics is understood at a higher level than elementary physics. Or it may perhaps mean that a thing is not reducible to the nature of its components. If the thing is in principle reducible but we do not actually ever bother to do the reduction then it is the same mundane statement. But if it means that the thing is in principle not reducible then it may still be mundane if the phrase is intended to mean, ‘by the nature of quantum mechanics, mathematical calculations and other restraints it is not in principle possible to actually reduce macroscopic systems to the behavior of their elementary particles even though the particles cause macroscopic properties’. Such mundane meanings hardly ever need to be stated (they are assumed) and if there is a need, than they can be clearly said.

 

On the other hand emergent properties can have a meaning that is anything but mundane. The phrase may imply upward causation. This is an odd idea – the whole causes behavior of the parts. For example, there is something unusual about the properties of consciousness that cause the properties of the parts of the brain (neurons, proteins, atoms etc.) to be what they are. Or the phrase may imply no material causation at all. For example, there can always or occasionally be no causal connection between the mind and the brain. These uses of emergent step outside of a physical/material universe and introduce a mysterious other substance/energy that is unknown, magic, spiritual or something – who knows.

 

So when I encounter someone referring to an emergent property, I am left thinking which is it: someone with conventional notions of the physical world but is leaving open the possibility that the reader can think he believes otherwise; or is it someone who does not have conventional notions of the physical world but is leaving open the possibility that the reader can think he does. Or maybe it is someone who thinks that the phrase sounds learned and is not saying or implying anything at all. I really try to be more generous and understanding but I find it very difficult. Emergent properties just pushes my buttons.

 

Unconscious learning under stress

ScienceDaily has an item (here) on a paper by L Schwabe, M Tegenthoff, O Höffken, O Wolf; Mineralocorticoid Receptor Blockade Prevents Stress-Induced Modulation of Multiple Memory Systems in the Human Brain; Biological Psychiatry, 2013. It examines the switch from conscious learning to unconscious learning under stress conditions.

 

 

Conscious learning involves the hippocampus and declarative memory while unconscious learning involves the dorsal striatum and procedural memory. Stress causes alterations of amygdala connectivity with hippocampus and dorsal striatum to shift the learning method towards unconscious learning. Performance in learning tasks that can be learned both ways do not appear to be affected by this shift.

 

 

The researchers used a weather forecasting ‘game’ to measure performance. The subjects can work out how to do the forecasting through trial and error, either with conscious problem solving or by going with their gut feeling. They found that by blocking a particular receptor type, mineralocorticoid receptors, this switch under stress by adrenal cortex hormones no longer happened and performance suffered as a result.

 

 

Here is part of the abstract:

 

Accumulating evidence suggests that stress may orchestrate the engagement of multiple memory systems in the brain. In particular, stress is thought to favor dorsal striatum-dependent procedural over hippocampus-dependent declarative memory. However, the neuroendocrine mechanisms underlying these modulatory effects of stress remain elusive, especially in humans. Here, we targeted the role of the mineralocorticoid receptor (MR) in the stress-induced modulation of dorsal striatal and hippocampal memory systems in the human brain using a combination of event-related functional magnetic resonance imaging and pharmacologic blockade of the MR.

 

Our findings indicate that the stress-induced shift from hippocampal to dorsal striatal memory systems is mediated by the amygdala, required to preserve performance after stress, and dependent on the MR.

 

 

It seems to me that learning during stress would be particularly important to survival but at the same time it may be that conscious resources are particularly stretched during stress – conscious learning might then be unreliable and moving learning to a more unconscious mode could be very advantageous. On the other hand there could be reasons for this that have to do with partially suppressing memories of stressful events so that the learning is not too painful to acquire. Perhaps it has to do with how the amygdala functions under stress as opposed to normally and is just one of a suite of related changes to memory under stress.

 

Meta-awareness

How good are we at knowing what we are thinking? Do we just know what we are conscious of because we have a memory of it that we can inspect? An interesting paper (citation below) examines our awareness of our mind wanderings. It seems that we often just miss the wandering entirely. So if I am concentrating on something and my mind periodically wanders off what I am trying to attend to then wanders back and I don’t notice – what does that say about my awareness of my ‘awareness’. (Of course I’m not aware of my blinks either.) By asking probing questions during tasks, it is possible to have subjects accurately report any mind wandering if it is happening. Or subjects can be asked to indicate when they notice mind wandering and this results in many mind wanderings being missed.

 

 

Why is mind wandering so easy to report but so difficult to spontaneously notice?

 

Converging evidence from behavioral, neurocognitive and combined paradigms indicate that, when prompted, people can accurately report whether or not they are mind wandering. By contrast, the spontaneous noticing of mind wandering, as assessed using both the self-caught/probe-caught methodology and retrospective classifications, indicates that individuals routinely mind wander without noticing this fact. A contributing factor to difficulties in noticing mind wandering may be that the experience can hijack the very brain regions that are necessary for recognizing its occurrence. Many of the brain regions engaged during mind wandering are implicated in systems that might be expected to contribute to the monitoring of the state itself. Accordingly, our persistent failure to catch ourselves mind wandering could occur because mind wandering occupies the precise brain regions that are necessary for noticing it. The hijacking of the following two processes could contribute to difficulties in noticing mind wandering.

 

1. Mental state attribution

 

Elements of the medial PFC (prefrontal cortex) are recruited both during mind wandering and in tasks that require theory of mind. Because mental state attribution involves the application of metacognitive processes to information of a stimulus-independent nature (e.g. inferences about the mental state of another individual), the engagement of these brain regions during SIT (stimulus-independent thoughts) could prohibit their utility in the service of catching the wandering mind.

 

2. Cognitive control

 

Periods of mind wandering also engage regions such as the dorsal ACC (anterior cingulate cortex ), which are known to be involved in error detection and conflict monitoring, and the anterior PFC, involved in cognitive meta-awareness. If mind wandering engages both metacognition and error-detection systems in the service of generating a coherent stream of SIT, then the fact that these systems are already engaged might make them less capable of detecting a mind-wandering episode. ”

ResearchBlogging.org

J Schooler, J Smallwood, K Christoff, T Handy, E Reichle, M Sayette (2011). Meta-awareness, perceptual decoupling and the wandering mind Trands in Cognitive Sciences, 15 (7) : 10.1016/j.tics.2011.05.006

Corrected link http://dx.doi.org/10.1016/j.tics.2011.05.006

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