The nuts and bolts of Parkinson's Disease.
Parkinson's disease (PD) typically manifests in individuals over the age of 50, with about 5% prevalence in those over 85 years old. Most cases are sporadic with rare inherited variants, suggesting that environmental or toxin-related triggers are likely contributors. PD is characterized by symptoms such as rhythmic tremors in the hands and feet, especially at rest, bradykinesia (slow movement), and akinesia (difficulty initiating movement). These symptoms result from damage and cell death in the brain regions such as the substantia nigra in the brain stem and the locus coeruleus, leading to decreased levels of norepinephrine and dopamine (DA). The substantia nigra projects to the striatum, where DA is the principal neurotransmitter involved in relaying movement messages to the cortex. Neuromelanin, a byproduct formed from the oxidation of DA to quinones and semiquinones and subsequent metal ion binding, is evident in PD due to its black pigmentation. The disease also features Lewy bodies in the substantia nigra and other brain areas, which are composed primarily of the protein alpha-synuclein, abundant in presynaptic neuron terminals. The major treatment for PD is L-DOPA, but excessive DA can lead to the formation of hydrogen peroxide and reactive oxygen species when released into the cytoplasm. This oxidative stress contributes significantly to the neurodegeneration observed in PDActive Sensing and Autism
In autistics, active sensing and multisensory integration can manifest differently compared to NTs. Research suggests that autistics may experience variations in how sensory information is integrated, leading to differences in perceiving and responding to the environment. For example:
- Hypo- and Hypersensitivities: Autistic individuals often exhibit sensory sensitivities that can affect their active sensing behaviors. Hypersensitivities (over-responsiveness) might lead to avoidance of certain sensory inputs, while hyposensitivities (under-responsiveness) might lead to seeking out more intense sensory experiences. This can affect how they use active sensing in daily interactions.
- Attention and Filtering: Differences in attentional mechanisms in autism can influence active sensing. Autistic individuals might have difficulty filtering out irrelevant sensory stimuli, leading to challenges in focusing on specific sensory inputs necessary for effective multisensory integration.
- Motor Coordination and Planning: Difficulties with motor coordination and planning, commonly observed in autism, can also impact active sensing. If motor actions are less precise or more effortful, it may affect the ability to actively manipulate sensory inputs effectively.
- Neural Processing Differences: Studies have shown differences in neural processing pathways involved in sensory perception in autism. Research has noted that autistic individuals might process sensory inputs in a more localized manner, potentially affecting the global integration of multisensory information (Marco et al., 2011)
- Predictive Coding: Some theories, such as those involving predictive coding, suggest that autistics might have a different approach to anticipating sensory inputs, which impacts how sensory information is integrated and processed. This can lead to differences in how expected and unexpected stimuli are managed, further influencing active sensing behaviors.
The Cocktail Party Effect
The "cocktail party effect" refers to the brain's ability to focus one's auditory attention on a particular stimulus while filtering out a range of other stimuli, as when a person can focus on a single conversation in a noisy environment. This ability involves the auditory cortex and other brain regions that manage attention. The term was coined by cognitive scientist Colin Cherry in the 1950s.
For example, at a busy party with multiple conversations happening simultaneously, you are able to listen and respond to one person speaking to you without being distracted by the surrounding noise. This phenomenon highlights our ability to selectively attend to particular sounds in a complex auditory landscape. It's often studied in contexts involving hearing, neuroscience, and psychology, particularly in understanding how attention and the sensory system interact.
In autistics, the cocktail party effect may manifest differently due to variations in auditory processing and attentional focus. Autistics often experience atypical auditory processing, which can mean that separating speech from background noise is more challenging. This difficulty is sometimes referred to as auditory filtering problems with "auditory scene analysis." Research suggests autistic children show diminished performance in tasks requiring them to attend to speech in noisy environments compared to their neurotypical peers (Alcántara et al., 2004). This can contribute to the sensory overload many autistic individuals report in noisy or crowded settings.
These auditory processing differences are an essential consideration in understanding the sensory experiences of autistic individuals and underscore the need for tailored strategies in educational, social, and occupational settings to accommodate their unique sensory profiles.
Interoception
Interoception refers to the perception and awareness of internal bodily states. It involves the ability to sense and interpret physiological signals originating from within the body, such as hunger, thirst, heartbeat, temperature, respiration, and the need for bodily functions. Interoception is crucial for maintaining homeostasis and overall well-being as it allows an individual to respond appropriately to bodily needs and emotional states. This internal sensory system plays a significant role in emotional experiences and self-regulation by linking physical sensations with emotional responses.
Relevance to Autism
For example, interoceptive awareness includes the ability to feel a racing heartbeat when anxious or to recognize a sensation of fullness to prevent overeating. In autism, this sense may be heightened or diminished, leading to unique challenges such as difficulty in identifying states of discomfort or illness, or misinterpreting signals of emotional changes which are critical in social interactions and personal health management. Moreover, the role of interoception in autism extends to fundamental daily activities; it influences everything from toilet training—where recognizing the need to urinate can be delayed or unclear—to managing anxiety and stress levels in response to overstimulation or environmental changes. These distinct interoceptive experiences can significantly affect how individuals with autism recognize and communicate their needs and emotions, thus requiring tailored strategies that address these sensory processing differences to enhance their quality of life and autonomy."
Alexithymia and Interoception
Stress and Neck Pain
The Accessory XI nerve, a cranial nerve, is vital for controlling the trapezius muscle, which facilitates various neck and shoulder movements. When stress occurs, this muscle can tense up, leading to neck discomfort. Interestingly, in quadrupeds like cats, the trapezius muscle is crucial for lifting the head; this adaptation aids grazing animals in responding to external stimuli. Additionally, the short-term memory (STM) muscles also contribute to raising the head, illustrating the complexity of our muscular system's evolution and functionality.
The Complex Terrain of Muscle Contraction - Insights from Disability
(Based on topic covered in Neuroanatomy Class along with some additional disability perspectives. )
In the world of biology, muscle contraction is a fundamental process, enabling us to move and function. The way our muscles contract, however, can lead to various consequences, especially when disrupted by factors like bacterial infections.
Muscle contractions are driven by motor units. Whether the contraction is strong or weak depends on how many of these units are activated. So a fine precise motor action requires small number of units activated and need little strength.
Understanding muscle pain takes us to the basics of cellular respiration. Muscles, like all cells, need oxygen, which is supplied through arteries. When a muscle contracts and restricts this oxygen supply, it creates a problem. The muscle cells continue to function, breaking down glucose in the absence of oxygen. However, this process produces lactate, leading to a burning sensation, indicating the body's distress.
This pain can have severe consequences. In intense muscle contractions, essential muscles like the diaphragm, responsible for breathing, can weaken. Chest muscles may become so tense that they hinder the natural process of inhaling and exhaling.
In the complexity of our body's workings, this delicate balance between muscle contraction and relaxation defines our abilities. Understanding these intricacies not only enhances our knowledge of our biological marvel but also emphasizes the need to appreciate and preserve the balance that allows us to move and function seamlessly.
There exists a parallel narrative, one that often goes unnoticed — the experience of autistics. Consider a autistic whose sensory perceptions are heightened and processed differently. The involuntary muscle contractions experienced by autistics might not only induce physical discomfort but also trigger heightened sensory responses, amplifying the distress. In such cases, the pain isn't merely a physiological phenomenon; it extends into the realms of sensory overload, creating an overwhelming and sometimes unbearable experience.
Consciousness
Nature of Consciousness and Quantum Physics. Both Sanathana Dharma and Buddhism assert that consciousness isn't a byproduct but a fundamental aspect of reality. This perspective aligns, to some extent, with certain interpretations of quantum mechanics, which propose that consciousness plays a role in the process of quantum measurement or wave function collapse.
Meditation, Mindfulness, and Neuroscience: Neuroscientific research into the effects of meditation—a practice central to both Sanathana Dharma and Buddhist traditions—has shown that it can induce significant changes in areas of the brain associated with attention, emotion regulation, and self-awareness.
Levels and States of Consciousness: The Mandukya Upanishad, outlines different states of consciousness, including waking, dreaming, deep sleep, and a transcendent state known as "Turiya." Modern neuroscience also explores various states of consciousness, such as REM sleep, deep sleep, and altered states induced by substances or meditation. Buddhist meditation practices often aim to transcend ordinary states of consciousness and attain enlightened states. Neuroscientific studies on accomplished meditators have reported unique brainwave patterns and states of consciousness.
Interconnectedness: Both Sanathana Dharma and Buddhist philosophies emphasize the interconnectedness of all things. This idea has resonances with holistic perspectives in science, especially in fields like ecology and certain interpretations of quantum physics which emphasize non-locality and entanglement.
Plasticity and Transformation: Both Sanathana Dharma and Buddhist traditions emphasize the possibility of transforming one's mind and consciousness. The idea of neuroplasticity in modern neuroscience—that the brain is malleable and can be changed through experiences, especially practices like meditation—aligns with this.
Phenomenal Experience: Buddhism, particularly in schools like Yogacara, delves deep into the nature of experience, cognition, and perception. These explorations find parallels in cognitive science and phenomenological approaches in modern philosophy of mind.
Phrenology according to Gall. A Historical Curiosity
The prevailing view of the era was dominated by religious or philosophical beliefs rather than empirical research. Gall's ideas challenged long-held beliefs about the nature of the mind and the brain and landed in a lot of hot water.
And the hot water was not just religions, but also social. Phrenology also had practical implications, as some individuals and organizations began using it for character assessment in various contexts, such as education and employment. This raised ethical and legal questions about the fairness and validity of making judgments about people based on phrenological assessments.
Gall's most notable contribution was his intricate neuroanatomy diagram, which depicted the brain as a series of localized faculties or organs, each responsible for a particular aspect of personality or behavior. The size of these organs corresponded to a person's character traits and abilities. Obviously this is quite incredulous by today's standards - a historical curiousity.
- Firmness (in frontal lobe) Development of this area in the frontal lobe was associated with determination, willpower, and the ability to persevere in the face of challenges.
- Immortality: linked to religious and moral tendencies, as well as a sense of spirituality.
- Veneration (Parietal Love): related to feelings of respect, admiration, and reverence for authority figures or ideals
- Destructiveness (in lower back of brain): aggressive and combative behaviors, as well as a propensity for violence.
- Benevolence (frontal love): linked to kindness, empathy, and a compassionate nature.
- Acquisitiveness (forehead): desire for material wealth and possessions.
- Wit (Frontal Lobe): responsible for humor, quick thinking, and cleverness.
- Love of Offspring (back of brain):linked to parental instincts and the love and care of one's children.
- Secretiveness (Upper back of brain): associated with the tendency to keep secrets and be discreet.
- Self-Esteem (upper back of head): related to self-confidence, pride, and a sense of self-worth.
The Brain is Never Zero
In the realm of thoughts, wonders reside
Brain pulses ceaselessly, a relentless tide
Neurons fire, synapses alight
The brain is never zero, its brilliance ignites.
EEG Capping
Felt like a soggy swim cap. Not the most comfortable feeling but tolerable.
To clarify, in this photo I'm trying on the cap to see what it feels like as I will likely be using neuroimaging methods (EEG, fMRI etc) in my own research design and I will be studying issues in autism.
Review v Meta Analysis
A meta-analysis is a specific type of research synthesis that involves combining and analyzing quantitative data from multiple studies to generate more robust conclusions. Researchers identify relevant studies, extract relevant data from each study, and statistically analyze the combined data to derive overall effect sizes or estimates of the relationship between variables. Meta-analyses often include a systematic review of the literature as a first step to identify relevant studies for inclusion.
Mental Time Travel
In this task, the individual's present moment serves as a reference point from which they situate and retrieve personal versus general events. Personal events refer to specific episodic memories from the individual's own life, such as a birthday party or a family trip, while general events are more abstract and can be shared by multiple individuals, such as historical events or holidays.
The MTT task taps into several cognitive processes and neural mechanisms associated with mental time travel. It requires the retrieval of specific episodic memories or the construction of plausible future scenarios. The task engages memory processes, including recall and recognition, as well as imagination and prospective thinking.
Neuroimaging studies have shown that the neural substrates underlying MTT involve a network of brain regions.
- PFC: cognitive control and executive function required for retrieving and manipulating temporal information.
- Hippocampus and MTL: formation and retrieval of episodic memories
The MTT task has been used in research to investigate individual differences in the capacity for mental time travel and how it relates to various cognitive processes, such as autobiographical memory, imagination, planning, and self-projection. It has also been employed to examine the effects of aging, neurodegenerative diseases, and psychiatric disorders on mental time travel abilities.
Depersonalization and Autism
- Loss of body ownership /disembodiment feelings / somatosensory distortions/ loss of agency: distressing feelings of being 'spaced out', detached from one's self, body, and the world (observing yourself from a distance).
- atypical 'flat' time perception (alterations in perception, including disruptions in the perception of time. )
Research findings on DPD and atypical time perception in the NT population
- Distorted perception of time: Tendency to overestimate the duration of time intervals, perceiving time as slower than it actually is which can contribute to the overall sense of detachment (1,2)
- Neural correlates of time perception: fMRI studies show differences in brain activity and connectivity patterns in regions associated with time processing, eg: PFC and parietal cortex (3,4)
- Role of attentional processes: Difficulties in allocating attention appropriately, leading to a reduced ability to accurately perceive and process temporal information (5,6)
- Emotional factors: Emotional states, eg anxiety and stress, can modulate time perception, leading to temporal distortions. DP folks often experience heightened levels of anxiety and emotional distress, which may contribute to their altered perception of time. (1,2)
- Both involve atypical sensory processing suggesting a potential shared underlying connection.
- Overlap in Symptoms: Though there are distinct dx criteria, both share some overlapping symptoms, such as a sense of detachment from oneself, difficulties with emotional regulation, and social challenges.
- Neurobiological Factors: Though the specific mechanisms and neural circuits may differ, both potentially involve alterations in brain functioning and connectivity.
- Impact on Functioning: Co-occurrence may exacerbate the challenges in everyday functioning especially in areas of social interactions and emotional well-being.
- 17% autistics met the diagnostic criteria for DPD, compared to 2% non-autistic (7)
- Compared to controls, autism+DPD more likely to have
- higher anxiety and depression (8)
- more difficulty with social interaction and communication (9)
- more repetitive behaviors and special interests (10)
Self Referencing and Self Projecting
- Self-Referencing: general capacity of using one's own position in time to estimate/situate events in time. This skill relies on internal cues such as memory and self-awareness to place events within a temporal framework. By referencing our own experiences and the temporal context in which they occurred, we can make sense of the timing and sequence of events in our environment.
- Self-Projecting: ability to mentally move back and forward in time, maintaining the competence of correctly situating events in time. This skill allows us to anticipate future events, plan our actions, and make decisions based on the temporal context. Self-projecting skill involves mental time travel, where we can mentally simulate and project ourselves into different points in time, drawing upon past experiences and knowledge to predict and shape future events.
Personal Space v PPS
[Concepts in Sensorimotor Research]
Personal Space v PPS
Personal space refers is a social construct - refers to the physical or psychological distance individuals prefer to maintain between themselves and others. It is the immediate area surrounding a person that they consider as their own.
Peri-personal space is a neuroscience construct to describe the area immediately surrounding the body that is within reach of the individual. It encompasses the space where individuals feel they can manipulate/reach using their limbs / body parts.
Past research has indicated autistics as having a very constrained PPS.
Principle of inverse effectiveness
Ergo, when the individual sensory cues are relatively weak or have low impact, the brain tends to rely more on multisensory integration to enhance the perception and processing of the stimuli. eg: people with hearing loss exhibit increased visual abilities, and increased crossmodal activation within the auditory cortex.
The principle of inverse effectiveness highlights the advantage of combining multiple sensory inputs in situations where the individual senses may provide limited or unreliable information. By integrating sensory cues from different modalities, the brain can enhance the overall perception and make more accurate judgments about the external environment. This principle has been observed across various species and sensory domains and is believed to reflect a fundamental property of multisensory processing.
MBNCA Connectome Dataset
https://www.biorxiv.org/content/10.1101/2023.03.10.532036v1
Interaural differences
- ITD (interaural time difference): time delay between the arrival of sound at each ear. ITD is greatest for sounds coming from the side of the head and is zero for sounds coming from directly in front or behind the listener.
- ILD (interaural level difference): amplitude difference between the sound waves arriving at each ear. ILD is greatest for sounds coming from directly to one side of the listener and is zero for sounds coming from directly in front or behind the listener.
Some studies have reported differences in how autistics process interaural differences, including reduced ability to integrate auditory and visual information, as well as altered auditory and multisensory temporal processing.