Neural Aging and the Shift Towards Conservative Beliefs
If you've ever been driving with an older person, you're likely to notice their diminished awareness of traffic conditions, and a general reduction in speed to compensate for it. Aging is not kind to neurological functions, as attention and visuospatial deficits get substantially worse with advancing age.
Two Famous Ex-LiberalsMany psychopharmalogical studies have documented the age-related decline of the monoamine transmitter systems--dopamine, noradrenaline, and serotonin. This is due primarily to the age-induced production of monoamine oxidase-B, an enzyme that breaks down the monoamine neurotransmitters.
There is evidence that the monoamine transmitter systems are distributed asymmetrically in the brain. The dopaminergic activation system is distributed asymmetrically in the left hemisphere, with its high signal-to-noise ratio forming the backbone of semantic language and fine motor control.
Conversely, the noradrenergic activation system is distributed asymmetrically in the right hemisphere, forming the backbone of attention and alertness, bilateral perceptual integration, and sensitivity to new and unusual stimuli.
We have proposed that these two activation systems contribute to significant variations in the behaviors and political attitudes of Conservatives and Liberals. Conservatives, on average, tend to exhibit behaviors and attitudes that are more dopaminergic.
Dopaminergic behaviors include such things as motivation, approach and exploratory behaviors, goal-seeking, unambiguous and contextual thinking styles, binary (Good vs Evil) morality models, and enhanced semantic and arithmetic reasoning. (Keep in mind that by arithmetic, we mean primarily addition and multiplication).
Liberals, on average, tend to exhibit behaviors and attitudes that are more noradrenergic. Noradenergic behaviors include such things as enhanced attention to environmental stimuli, aversive behaviors, more ambiguous and non-contextual thinking styles, enhanced susceptibility to anxiety and depressive disorders, empathetic and non-binary morality models, and artistic creativity.
Both Conservatives and Liberals exhibit tendencies of both of these activation systems. However, the cognitive evidence indicates a distinctive shift, on average, of Conservatives towards the dopaminergic side, and Liberals towards the noradrenergic side.
However, there is also evidence that the two hemispheres of the brain do not age uniformly. Most notable is the rapid decline of visuospatial reasoning, (asymmetrically distributed in the right hemisphere), relative to linguistic processing (asymmetrically distributed in the left).
There are two notable models of hemispheric aging, the Right Hemi-Aging model, which proposes that the right hemisphere exhibits a greater age-related decline than the left, and Cabeza's Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model, which proposes that frontal cortex activity is less lateralized in older than in younger adults.
While these two models are not mutually exclusive, they are broadly framed, and do not delineate the specific regions of each hemisphere that age asymmetrically, or the even the age ranges associated with this decline. As a result, there is a lot of contradictory evidence, especially in studies that do not control for gender.
As early as 1958, Wechsler reported visuospatial deficiencies in the elderly as related to younger adults. However, there was little or no decline in verbal and language comprehension tests between the elderly and young. Older people continue to do relatively well with language, but attention and visuospatial analysis are strongly compromised.
The cognitive evidence would finally be augmented with brain imaging in 1994, when Grady et al found that the occipitoparietal and occipitotemporal cortical regions were less active in older people. These two regions are usually activated during a variety of visuospatial tasks.
Older people were having trouble utilizing the occipital cortex and were more likely to incorporate the prefrontal cortex (PFC) to make up for the deficit. This enhanced reliance on the PFC for visuospatial analysis would cause a corresponding reduction in reaction times. Later, Grady would notice an age-related shifting to the left PFC for certain facial recognition tasks, and a corresponding decrease in activity in the right PFC.
While there was an observed decrease in right PFC activity for visuospatial tasks, Anderson et al noticed something very interesting during a word-pair encoding task--the left PFC activity declined in older subjects. But what was truly remarkable was the corresponding increase in right PFC activity during the same word-pair encoding task. Was the right hemisphere improving in its ability to process language? Was the left hemisphere losing its ability?
Word recognition studies would also show variations in hemispheric processing with age. Word recognition is primarily right-lateralized in young people, and tends to become more bilateral with advancing age. While this seems to be contrary to the idea of a relative improvement of the right hemisphere in language processing, word recognition is actually consistent with the right hemisphere's general advantage in visuospatial processing. Words are processed as holistic shapes just like any other object in the right hemisphere.
Older people were also more negatively impacted with context memory than with item memory. This points to the shifting of the right PFC from managing contextual memory retrieval, to other functions such as compensating for perceptual processing deficits.
In our Spring 2005 survey, we noted several age-related cognitive shifts that are consistent with the theory that the right hemisphere behaves more like the left hemisphere for certain mental functions.
We found evidence of a relative improvement of language comprehension in the right hemisphere for people over 25. We have found a significantly greater reliance in the elderly on left ear phone conversations than younger people. This left ear presents auditory stimulation asymetrically to the right hemisphere.
From Under 25 to Over 60, the shift to left ear preference for phone conversation more than doubles (from 26% to 56%). This shift is accentuated in right handers, presumably because it frees up the right hand for other tasks.
We find concurrent evidence with our shape versus semantic word test, which requires that the subject indicate a preference of shape versus semantic translation for a word pair. The preference for shape drops from 27% for our Under 25 cohort to just 14% for our Over 60 cohort, providing further evidence of an age-related deterioration in spatial versus language performance. Further, there is a noted decrease, from 44% in our Under 25 cohort to just 29% in our Over 60 cohort, for subjects reporting difficulty in maintaining attention while listening.
But the most politically relevant evidence is the binary morality model preference (e.g., good vs evil) that increases from 10% for the Under 25 group to 29% for the Over 60 age cohort in Liberals.
Interestingly, Conservatives exhibit no change in binary morality model preference with advancing age (79% with the Under 25 cohort and 79% with the Over 60 cohort). This shifting of Liberals towards binary morality models is significant, and indicative of a decrease in ambiguity in Liberal cognitive styles as they age.
Discussion
What is going on in the brain as it ages? There have been numerous theories, many involving neuronal, synaptic, and neurotransmitter deterioration. However, there is still no widely accepted neural theory of age-induced cognitive deficits. Indeed, a true picture will most likely involve a combination of many diverse neural components.
The cognitive evidence is consistent with a more rapid deterioration in sensory system processing relative to linguistic processing. This may imply that the decline in the noradrenergic activation system is reducing crosstalk and network interference in semantic language networks, which seem to be impacting the right hemisphere in particular.
However, the deterioration of the dopaminergic system is also prominent, and the clinical evidence of the asymmetric aging of these two activation systems is not unequivocal. Indeed, there are many possible neural deterioration models that will fit the cognitive deficits we have discussed.
But it appears that the right hemisphere is behaving more like the left hemisphere with advancing age. Indeed, we find a significant age-induced shift towards organized and unambiguous binary morality models in the Liberal, which is highly correlated with political conservatism and traditional religious beliefs. Liberals usually report a very low preference for good versus evil models of the world, but the Over 60 age group is the lone exception.
An aging population appears to be a more conservative population, all other things being equal.
Empathetic Neural Networks That Moderate Goal-Seeking in Conservatives and Liberals
(Part 3 of Political and Sexual Arousal in Conservatives and Liberals)
In our Fall 2005 survey, we encountered a high correlation with how much time people spend thinking about both politics and sex. Is this just an idle coincidence, or are political and sexual arousal more than just strange bedfellows?
The Left Prefrontal Cortex Activated During a Mental Reordering of Lists in Working MemoryThe survival value of both sexual and political behavior require the brain to devote a correspondingly large number of neural resources in their execution. The brain's propensity to transfer different functional information across reusable neural network components is analogous to how information is packaged and transferred along modern day multinodal computer networks.
While there is a significant degree of neuronal specialization and single-tasking, (particularly for such things as the autonomic control of visceral processes), emotional and cognitive neural network components are widely distributed, malleable, and even reusable for a variety of functions.
But the analogies between computers and the brain do not stop with processing information across distributed networks. Another computer concept related to the functioning of central processing units is working memory, and has become an important part of the lexicon of neuroscientists.
The concept of working memory was pioneered by Baddeley, when he sought to explain Miller's research that the human brain could handle about seven pieces of concurrent information in what was then thought to be short-term memory. However, the duration of this memory was about 10 seconds, and short-term memory was therefore regulated by different neural mechanisms than working memory.
Borrowing heavily from computer terminology, the working memory advocates proposed the existence of a common temporary storage system, or common set of memory buffers. Each sensory system has at least one buffer, which, like any computer input-output buffer, can be used to queue up sensory information for a slight delay in processing.
Caramazza et al suggested that the brain maintains an input auditory-verbal buffer that holds onto phrases just heard so they can be semantically parsed. Your ability to process someone's sentence a few moments after it is uttered is due to this auditory-verbal input buffer. They also proposed a phonological output buffer that stores the words you are about to say.
Baddeley proposed the existence of a visuospatial scratchpad, used to hold certain types of visual information for a short period of time for extended perceptual analysis. As the list of sensory and motor system buffers grew to account for the mounting experimental and clinical evidence, the obvious implications of these working memory theories were in their relationship to the Holy Grail of all neuroscience---consciousness.
Theories of consciousness popped up quickly, and the management of working memory was a cornerstone in many of them. The contents of working memory are what the brain is paying attention to--but more importantly, what areas in the brain are paying attention to working memory?
The lateral prefrontal cortex (LPFC) has been implicated in the executive management of working memory. The LPFC has quite an impressive array of connections to the auditory and visual systems, spatial and verbal working memory systems, long-term memory systems, and remarkably, the motor cortex.
The connections to these systems are bi-directional, which allows the LPFC to tune the sensory, working, and long-term memory systems to focus on selected targets. But a portion of the lateral prefrontal cortex is of particular interest--the orbital region. The orbital region resolves whether a stimulus is good or bad, and decides whether that stimulus has resulted in a reward or punishment.
The orbital prefrontal region is further connected to the amygdala and anterior cingulate, which are part of the brain's emotional "limbic" system. Lesions to the orbital prefrontal cortex can result in sociopathic behavior and a general inability to resolve emotion in others.
But like most neural structures that are located in both hemispheres, their behavior is asymmetric. The left LPFC has been more implicated in task switching, but not in the performance of multiple tasks at once (this seems to be controlled by the bilateral intra-parietal sulcus region). The left LPFC has also been more implicated in reducing the activation of the amygdalae.
This important function contributes to the linguistic functioning of the left hemisphere by improving the verbal reasoning processes that can be disrupted by an active and emotional amygdala. The left LPFC also contributes more towards reward-seeking and exploratory behavior. The right LPFC is more activated during threat assessment and in limiting reward-directed behavior. The left prefrontal cortex is also more involved in semantic processes, and the right in non-semantic processes.
There is clinical evidence that the orbital prefrontal cortex functions asymmetrically as well. Lesions to the left orbital prefrontal cortex result in less reward-seeking behaviors, and lesions to the right result in more. The asymmetrically distributed dopaminergic system in the left hemisphere is engendering this specialization, as is the asymmetrically distributed noradrenergic activation system in the right.
Now that we have a crude model of some of the neural substrates of consciousness, let's return to the cognitive evidence on political and sexual arousal from our Fall survey.
The concept of political arousal is a little misleading, as it encapsulates the activity of the regular arousal systems, such as the cholinergic, dopaminergic, noradrenergic, and serotonergic, as they respond to political subjects or events. For example, let's take oil exploration in the Arctic National Wildlife Refuge as a political subject.
Some people will react strongly to this subject, and others will have no reaction. The highest levels of arousal will be at the two ends of the political spectrum -- the Very Conservatives and the Very Liberals.
As we noted in last month's edition, the further one varies from middle-of-the-road political preferences, the more time one is likely to spend thinking about politics. We propose that the dopaminergic and noradrenergic activation systems are principally responsible for the political arousal to this subject, due to the goal-seeking nature of the activated dopaminergic system, and the empathetic nature of the activated noradrenergic system.
Indeed, there are numerous such political subjects that place goal-seeking and empathy against each other, and it is just these subjects that get a lot of attention from Conservatives and Liberals. But let's look again at the orbital region of the prefrontal cortex (PFC).
This is the region that moderates both reward and punishment--and emotional recognition. It has deep hooks with the amygdala and anterior cingulate, two structures implicated in emotional response, empathy, and reward anticipation.
It is the orbital region of the PFC that is a principal neural suspect in the variation of Liberal and Conservative political attitudes in the cases where reward-seeking is pitted against empathy. It is this region that consolidates both empathetic and reward-seeking neural inputs, and outputs a decision. As would be expected, evolution has put these two motivations into the same neural decision networks--providing socially-mediated self-regulation on personal reward-seeking behavior.
The priming of the orbital region by the dopaminergic arousal system is a principal input that biases the region to favor reward-seeking against empathy in situations when they are mutually exclusive. Conversely, we propose that the noradrenergic arousal system primes the orbital PFC towards empathetic decisions when they are pitted against reward-seeking.
In other words, the same neural mechanisms that cause political arousal are the same mechanisms that shape the decision related to that political arousal. The more someone is politically aroused, the less likely they will take middle-of-the-road political positions. This was a very prominent characteristic of the cognitive evidence from our Fall 2005 survey.
While we have implicated a variety of neural structures and arousal systems in our political arousal neural network, such as the LPFC (the orbital region in particular), the amygdala, the anterior cingulate, and the dopaminergic and noradrenergic activation systems--the neural networks are more widely distributed than the aforementioned structures.
Personal reward or goal-seeking is self-regulated by at least three mechanisms: empathy, morality, and religiosity. While the neural networks underlying these three mechanisms share many common neural substrates, individuals, (males in particular), are more likely to favor one over the others.
But issues that pit goal-seeking and empathy against each other are not the only category of issues that will cause attitudinal variations between Conservatives and Liberals. One such issue is sexual behavior--one of the most interesting of all attitudinal variations.
Liberal males have the highest rate of sexual awareness, yet the lowest rate of procreative efficiency. The Very Religious Conservatives have the lowest rate of sexual awareness, yet the highest rate of procreative efficiency. They also have their children at a younger age.
We will discuss the neurosexual networks that may explain these behaviors and the curious role that religiosity plays in executing sexual behavior in the final installment of this series.
Brack and Zhang, January 2006
Email: Brack@neuropolitics.org
Zhang@neuropolitics.org
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Liberalism and the Noradrenergic Activation System
Humans are not the only animal that exhibits liberal and conservative behaviors--many social animals exhibit their own variation on conservatism and liberalism. Indeed, human political preferences are the natural evolution of primate social behavior.
The Noradrenergic Activation SystemIn last month's edition, we discussed one of the primary neural networks that account for many Conservative behaviors and attitudes--the dopaminergic activation system. The dopaminergic activation system is well organized into three major pathways in the brain, and is responsible for such behaviors as goal-seeking and unambiguous cognitive styles. We have proposed that the strong preference for freedom originates from the dopaminergic system, as freedom minimizes interference with goal-seeking behaviors.
But reward-seeking dopaminergic behaviors can create conflict in competitive situations, and need to be properly integrated into social contexts. Goal or reward-seeking behaviors would have to be evaluated in the context of the potential threats coming from other humans--particularly organized groups of other humans.
Evolution would throw a lot of neural resources at moderating the risks associated with the dopaminergic system's natural tendency for unregulated goal-seeking. One of those resources was the dopaminergic system itself.
Indeed, it is tempting to speculate that the development of moral and religious attitudes were in part the dopaminergic system's answer to its own propensity for socially competitive reward-seeking. Many religious rewards are substantial, non-worldly, non-competitive, and obtained after death. This transfers worldly reward-seeking to heavenly.
One of the social impacts of religious reward-seeking, instead of worldly reward-seeking, was to reduce intra-group competition. We do have some evidence of a reduction in the reported rates of competitiveness among the Very Religious from our Summer 2005 survey. Strong religious tendencies, based on our preliminary cognitive evidence, reduce competitive reward-seeking.
While the dopaminergic activation system has evolved into the promotion of morality and religiousness to provide social controls on its own tendency for reward-seeking, two other neurotransmitter systems would also do much to integrate dopaminergic reward-seeking into socially acceptable behaviors--the noradrenergic and serotonergic activation systems.
Dopamine, noradrenaline, and serotonin are well organized into separate systems that originate from subcortical regions of the brain. The neuronal cell bodies that produce these respective neurotransmitters have axons that project into a variety of cortical and subcortical structures. (See the above diagram of the main noradrenergic projections).
These three neurotransmitter systems regulate a variety of specific behaviors, and we propose them to be principally responsible for many behaviors and attitudes that are categorizable under Liberal and Conservative designations.
The noradrenergic activation system (NAS) is of particular significance in regards to Liberal cognitive styles and behaviors. Noradrenergic neurons in the locus coeruleus (LC) and the lateral tegmental nucleus (LTN) project throughout the cortex, hippocampus, thalamus, amygdala, septum, and other mid-brain structures. The NAS is important in attention, arousal, and the management of the sympathetic nervious system, which regulates fight or flight responses to environmental cues.
The locus coeruleus and lateral tegmental nucleus are two of the major stress-responsive regions in the brain. However, there is some evidence that the LTN is more involved than the LC in negative motivational states and aversive behaviors. This is consistent with the Liberal's lower propensity for competitive goal-seeking behaviors. This is also consistent with the Liberal's elevation in reported depressive and anxiety disorders.
Indeed, the LTN is plugged into the amygdala, a structure more activated in Liberals during recent fMRI research by Iacoboni. Noradrenaline networks seem to be critical in resolving negative mood states in others, and form the backbone of empathy processing. But noradrenaline networks have an interesting ability to selectively amplify stimuli and modulate that amplification over time.
This, along with the generally lower signal-to-noise ratio and wider dispersion of the axonal components of noradrenergic networks, leads to another interesting cognitive characteristic of Liberals--more ambiguous thinking styles.
The noradrenergic activation system is distributed asymmetrically in the right hemisphere, and the dopaminergic in the left---which at least partially explains the cognitive evidence of hemisphericity variations in Liberals and Conservatives. There is also some evidence of a common regulator of these two transmitter systems---an adrenergic system---which may be selectively activating the noradrenergic and dopaminergic systems.
But the noradrenergic and dopaminergic systems are not the only players in political behavior. The serotonergic system, the prefrontal and temporoparietal cortices, and the hormonal axis (in particular the sex hormones), are also strong influences on political attitudes. We will begin our discussion on the political contribution of the serotonergic activation system in a future edition.
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Female Visuospatial Performance Deficits in the Very Religious
We've encountered a rather dramatic result from our lone visuospatial test in our Winter 2006 survey that warrants some discussion. In our October 2005 edition which featured the article Visuospatial Task Performance, Binary Morality Models, and Religious Tendencies, we provided evidence of a significant decline in visuospatial performance in the Very Religious females.
In the same article, we noted that this decline was not as pronounced in the Very Religious males, and only impacted those Very Religious males that exhibited a strong preference for binary morality models (good vs evil).
In the Winter 2005 survey, we asked the question How often do you think about God? The survey participant would select one of five different responses: constantly, frequently, sometimes, little, and never. The percentages of these respective cohorts with the correct answer in the visuospatial task are shown in the graph below, and based on 1,495 total responses.
Percentages with Correct Answer by How Much They Think About God (M=Male, F=Female) (Constant=Constantly, Freq=Frequently)Those females indicating that they think constantly about God do no better than random chance (31%) in our visuospatial task. Those females indicating frequently do substantially better, but still beneath those indicating that they think about God sometimes, little, or never.
The males that think constantly about God do much better than their female counterparts, but still beneath all other males. Note that the males exhibit a consistent elevation in performance as they think less about God.
This is the third consecutive survey where the Very Religious females scored significantly lower in our visuospatial tests. Even though visuospatial testing results are not very reliable, the probability that Very Religious females have visuospatial reasoning deficits is very high.
So what has happened to the Very Religious female's ability for visuospatial analysis? Has it become adapted into religious cognition? Or have the right hemispheric temporoparietal regions and visuospatial scratchpad been suppressed by homologous regions in the left hemisphere, which are adapted into the Very Religious female's constant focus on God?
But the constantly focused female has some very interesting attributes that set her apart from other females: higher birth rates, lower rates of conscious sexual awareness, lower age at birth of her first child, and higher rates of phobias. These are important clues for further research and discussion.
