NEURAL ENGINEERING UNIT 4 FUNCTIONAL NEUROIMAGING AND RECOGNITION
- 1. KONGUNADU COLLEGE OF ENGINEERING AND TECHNOLOGY (AUTONOMOUS) NAMAKKAL- TRICHY MAIN ROAD, THOTTIAM DEPARTMENT OF BIOMEDICAL ENGINEERING 20BM708PE – NEURAL ENGINEERING (REGULATION-KNCET - UGR2020) UNIT IV – FUNCTIONAL NEUROIMAGING AND RECOGNITION Ms. M. Thendral, Assistant Professor / BME KNCET
- 2. UNIT IV FUNCTIONAL NEURO IMAGING AND RECOGNITION •Historical and physiological perspective, Function neuroimaging methods: PET and fMRI, Network Analyses, Functional neuroimaging of Attention, Visual recognition, Semantic memory, Inv Language, Episodic memory, Working memory, Cognitive aging, Neuro-psychologically impaired patients.
- 3. HISTORICALAND PHYSIOLOGICAL PERSPECTIVE • Early Foundations (19th-early 20th century): The origins of functional neuroimaging can be traced back to brain stimulation experiments conducted in the 1870s. They discovered that electrical stimulation of specific brain areas in animals led to motor responses. This laid the groundwork for understanding localized brain functions. • Electroencephalography (EEG) (1920s): EEG in the 1920s, recording electrical brain activity using electrodes placed on the scalp. This allowed researchers to study brain rhythms and changes in electrical patterns associated with different cognitive states. • Positron Emission Tomography (PET) (1950s-60s): PET emerged in the 1950s with the development of the first positron-emitting isotopes. In the 1960s, PET is used to visualize brain activity by detecting the distribution of radioactive tracers injected into the bloodstream. PET provided insights into brain metabolism and function.
- 4. HISTORICALAND PHYSIOLOGICAL PERSPECTIVE • Functional Magnetic Resonance Imaging (fMRI) (1990s): The 1990s brought a significant breakthrough with fMRI. Blood oxygenation level-dependent (BOLD) signals could be measured using MRI scanners, allowing researchers to indirectly infer brain activity based on changes in blood oxygen levels. This method provided a non-invasive way to map brain function with higher spatial resolution than PET. • Advancements in fMRI (2000s): Over the 2000s, fMRI technology improved, enabling higher-resolution images and more sophisticated analyses. Techniques like resting-state fMRI emerged, allowing researchers to study brain connectivity patterns even when the brain isn't engaged in specific tasks. • Magnetoencephalography (MEG) (1960s-70s): MEG measures the magnetic fields generated by neural activity. MEG offers excellent temporal resolution and helps researchers understand the timing of brain processes. • Near-Infrared Spectroscopy (NIRS) (1970s-80s): NIRS measures changes in blood oxygenation similar to fMRI but uses near-infrared light. This method, initially used in cardiovascular research. NIRS is portable and is often used for studies involving infants or patients with mobility limitations.
- 5. FUNCTION NEUROIMAGING METHODS: PET SCAN •PET scan is a type of nuclear medicine imaging. PET scan that can image biological and chemical activities. PET scanner is used to produce an image showing the distribution of tracer in the body. PET is an image modality that produce 3D imaging of the body that are capable of demonstration of the Biochemical function of body’s organ and tissues •A positron emission tomography (PET) scan is an imaging test that allows doctor to check for diseases in your body. The scan uses a special dye containing radioactive tracers. These tracers are either swallowed, inhaled, or injected into a vein in your arm depending on what part of the body is being examined. Certain organs and tissues then absorb the tracer.
- 6. FUNCTION NEUROIMAGING METHODS: PET SCAN Principle PET is uses radiotracer or pharmaceutical fluorodeoxy Glucose (FDG). Firstly, FDG is injected intravenously into the patient. FDG emits positron by going into the patient’s abnormalities or malignancy tissue. Half-life of positron is very short. FDG is similar to our glucose molecules and travel in the body same way as glucose and undergoes metabolism.
- 7. FUNCTION NEUROIMAGING METHODS: PET SCAN If the tissue is normal this process continues during metabolism. If there is any malignancy presence of pathology infection and other abnormality, the FDG gets trapped. FDG emits positron from abnormal tissue. The emitted positron joins with an electron and undergoes annihilation. The positron annihilation produces 2 photons of energy 511KeV (Kilo- electron Volt) each emitted in opposite direction (180 degree) in the body site. The photo detector by a set of rings detectors surrounding the patient. The detectors send these signals to the computer and the computer create the final image from these signals.
- 8. FMRI SCAN • Functional Magnetic Resonance Imaging (fMRI) is a neuroimaging technique used to measure and map the brain's activity by detecting changes in blood flow and oxygenation. It is a non-invasive and powerful tool for studying brain function and has a wide range of applications in neuroscience and clinical research. Principle: • fMRI is based on the principle that changes in neural activity are associated with changes in blood flow and oxygen levels in the brain. When a particular brain region becomes more active, it requires more oxygenated blood. This increased blood flow is detected by the Blood Oxygenation Level Dependency (BOLD) Contrast: • The BOLD effect is a key principle in fMRI. It is based on the fact that oxygenated and deoxygenated haemoglobin respond differently to magnetic fields. When a brain region becomes active, there is an increased demand for oxygen. Blood flow to that region increases, but oxygenated haemoglobin concentration decreases. The change in the magnetic properties of blood due to this oxygenation change is detected by fMRI.
- 9. FMRI SCAN Detection of Signal Changes: • The fMRI machine detects the changes in MR signal intensity that result from alterations in blood oxygenation levels. Regions with increased neural activity show a corresponding increase in blood flow, leading to a higher MR signal. Temporal and Spatial Resolution: • fMRI provides both temporal and spatial information. Temporal resolution is relatively moderate, capturing changes in brain activity over a few seconds. Spatial resolution, on the other hand, is quite high, allowing researchers to pinpoint activity to specific brain regions.
- 10. NETWORK ANALYSES • Network analyses of functional neuroimaging involve studying the brain's functional connections and interactions using techniques like fMRI or EEG. It analyses patterns of activity to understand how different brain regions communicate and work together to perform various cognitive functions or tasks. These analyses provide insights into brain organization, information flow, and can help uncover neurological conditions. • Data Acquisition: This is the initial step where functional neuroimaging data is collected using techniques like fMRI (functional magnetic resonance imaging) or EEG (electroencephalography). • Preprocessing: Raw imaging data undergoes preprocessing to correct for artifacts, noise, and align it spatially and temporally. • Region of Interest (ROI) Extraction: Brain regions are identified and isolated from the imaging data. These regions will be used as nodes in the network. • Functional Connectivity Calculation: Measures of functional connectivity, such as correlations or coherence, are calculated between the time series of different brain regions. • Network Construction: Using the connectivity measures, a network is constructed where nodes represent brain regions and edges represent the strength of functional connections between them.
- 11. NETWORK ANALYSES • Graph Theory Analysis: Various graph theory metrics, like degree centrality, betweenness centrality, and clustering coefficient, are calculated to quantify network properties. • Community Detection: Nodes within the network are grouped into communities or modules based on their connectivity patterns. • Statistical Analysis: Statistical tests are applied to identify significant differences in network properties between conditions, tasks, or groups. • Visualization: Network visualization techniques are used to represent the brain's functional connectivity as a visual graph, aiding in the interpretation of results. • Interpretation: Researchers interpret the network's topology, identifying key hubs, pathways, and connectivity patterns relevant to the study's objectives. • Clinical or Cognitive Correlations: The identified network features are related to cognitive functions or clinical conditions to draw meaningful insights. • Validation and Replication: Results are validated using additional data or by replicating the study in different populations to ensure the robustness of findings.
- 12. FUNCTIONAL NEUROIMAGING OFATTENTION Functional neuroimaging of attention involves using various techniques such as fMRI (functional magnetic resonance imaging) and EEG (electroencephalography) to study brain activity while individuals focus their attention on specific tasks or stimuli. These techniques allow researchers to identify brain regions and networks associated with attention processes and gain insights into how attention functions at a neural level. The procedure for functional neuroimaging of attention typically involves the following steps: Task Design: • Researchers design a task that requires the participant's attention, such as a cognitive task, visual task, or auditory task. The task is carefully constructed to manipulate different aspects of attention, such as selective attention or sustained attention. Participant Preparation: • The participant is prepared for the neuroimaging session. They may be provided with instructions about the task and the imaging environment. For fMRI, participants are positioned inside the MRI scanner, while for EEG, electrodes are placed on their scalp.
- 13. FUNCTIONAL NEUROIMAGING OFATTENTION Data Acquisition: • a. fMRI: Functional MRI measures changes in blood oxygenation levels as an indirect measure of neural activity. Participants perform the attention task while their brain activity is recorded using the MRI machine. • b. EEG: Electroencephalography records the electrical activity of the brain using electrodes placed on the scalp. Participants engage in the attention task while their brain's electrical signals are captured. Data Analysis: • a. fMRI: The acquired fMRI data are processed to create functional brain maps that show areas of activity during different attention states. Statistical analyses help identify regions that are more active during specific attention conditions. • b. EEG: EEG data are analysed to extract event-related potentials (ERPs) or oscillatory activity related to attention. Signal processing techniques reveal patterns of brain activity associated with different attentional processes. Interpretation: • Researchers interpret the results to understand how attention is modulated in the brain. They identify activated brain regions or networks linked to specific attentional tasks, providing insights into the neural mechanisms underlying attention.
- 14. VISUAL RECOGNITION • Visual recognition, also known as computer vision, is a field of artificial intelligence (AI) that focuses on enabling computers and machines to interpret and understand visual information from the world, such as images and videos. The primary goal of visual recognition is to replicate human visual perception and cognition, allowing computers to extract meaningful information from visual data. • In the context of deep learning for visual recognition, the process involves several stages: input, convolution, pooling, classification, and output. This process is commonly used in convolutional neural networks (CNNs) for tasks like image classification and object detection.
- 15. MEMORY TYPES
- 16. Sensory Memory: This type of memory holds sensory information for a very brief period, typically less than a second. It includes iconic memory (visual) and echoic memory (auditory).
- 17. Echoic memory •Echoic memory is a type of sensory memory that specifically refers to the temporary storage of auditory information or sound. •It allows us to briefly retain and recall sounds or spoken words that we have just heard, typically for a few seconds.
- 18. Iconic memory •Iconic memory is a type of sensory memory that pertains to the temporary storage of visual information or images. •It refers to the ability to briefly retain and recall visual stimuli that we have just seen, typically for a very short duration, often less than a second.
- 19. Tactile memory/ Haptic memory • Haptic memory, also known as tactile memory, refers to the temporary storage and recollection of tactile or touch sensations. • It allows us to remember the feeling of objects we have touched or textures we have experienced for a brief period of time.
- 20. Types of memory Long-Term Memory (LTM): LTM can store information for an extended period, ranging from minutes to a lifetime. It has a vast capacity and includes declarative memory and non-declarative memory. Declarative Memory: This includes facts and events that can be consciously recalled, such as episodic memory (specific events) and semantic memory (general knowledge).
- 21. Types of memory Non-Declarative Memory: This includes skills, habits, and conditioned responses that are typically not consciously controlled, like procedural memory (skills) and classical conditioning. Episodic Memory: Episodic memory is a subcategory of long-term memory that stores personal experiences and events in a chronological order.
- 22. Types of memory Semantic Memory: Semantic memory is another subcategory of long-term memory that stores general knowledge, facts, and concepts. Procedural Memory: Procedural memory is a type of non- declarative memory that stores information about how to perform various tasks and skills.
- 23. Types of memory Short-Term Memory (STM): STM holds information for a short duration, usually around 15-30 seconds. It has limited capacity and is often associated with working memory. Working Memory: This is a system that temporarily holds and manipulates information needed for cognitive tasks. It's closely related to short-term memory.
- 24. SEMANTIC MEMORY • Semantic memory is a Category of long-term memory that involves the recollection of ideas, concepts and facts commonly regarded. as general knowledge. Examples of Sematic memory include factual Information such as grammar and algebra. • Semantic memory different from episodic memory in that while sematic memory involves general knowledge, episodic memory involves personal life experiences. • there is much debate concerning the brain regions at work in the function of Semantic memory. While a Semantic network graphically represent relationships between the various concepts, sematic Satiation refers to a phenomenon wherein repetition results the temporary loss of meaning. • A Semantic memory is a type of long-term declarative memory that refers to facts Concepts and Ideas which we have accumulated over the course of our lives. • Sematic memory generally encompasses matters widely constructed as Common knowledge, which are neither exclusively nor immediately drawn from Personal experience.
- 25. SEMANTIC MEMORY Sematic Network • A Semantic network is a Cognitively based graphic representation of knowledge that demonstrates the relationships between various Concept within a network. A taxonomic hierarchy may order the organization of a nodes. a Semantic network's areas and nodes. A node is a Symbol that represents specific word, feature or concept whereas an arc is a Symbols that stands for a two-place relationship between nodes. • Unlike neural networks, Semantic networks are unlikely to use distributed. A Semantic network can be either a directed of an undirected graph. while the vertices there in would represent concepts, the edges would stand for the Sematic relations between the Concepts.
- 26. EPISODIC MEMORY Episodic memory is the form of memory that allows an individual to recollect happenings from his & her past. Two Senses of episodic memory. episodic memory task episodic memory System. Episodic memory task • If it is not possible to retrieves information other than through recollecting a specific episode, a task is considered an EM task. By this rule, conventional recall recognition tasker in which the rememberer must produce the name or identify as old a copy of an item encountered on earlier occasion in a particular situation are classified as episodic.
- 27. EPISODIC MEMORY Episodic memory System • Neurocognitive System is supposedly specific to episodic memory as opposed to other memory system. Eg: Semantic & procedural memory. Only by virtue of an intact brain system specialized for the purpose can me access episodic memory, • Time period of episodic memory system • The typical EM take only top on specific section of the entire EM system, namely those on a micro or medium time scale. The entire system also includes long lasting FM such as long term episodic memory, Sometimes called autobiographic memory, memories of personal past experiences such as first school day, and accidents.
- 28. Working memory • Working memory is a cognitive system responsible for temporarily holding and manipulating information needed for various cognitive tasks, such as problem-solving, decision-making, and language comprehension. • It's often described as the brain's "workspace" where information is actively processed before being stored or forgotten. • Working memory plays a crucial role in everyday activities like mental arithmetic, following directions, and reading comprehension. • It's distinct from long-term memory, which involves the storage of information over a more extended period.
- 29. Working memory
- 30. Working memory Sensory Memory • Records information from the senses for up to three seconds- Examples are Iconic (Visual) Memory and Echoic (Auditory) Memory Short-Term Memory • Holds about seven items for up to twenty seconds before the material is forgotten or transferred to long-term memory Long-Term Memory • Relatively permanent, can hold vast amounts of information
- 31. Phenomena explained by Working memory Phonological confusion Irrelevant speech effect Word length effect
- 32. Phonological confusion •Phonological confusion refers to the tendency to mix up or confuse sounds, syllables, or words that are similar in terms of their phonological properties. •Phonology is the study of the sounds that make up language, and phonological confusion can occur in both spoken and written language.
- 33. Irrelevant speech effect •The irrelevant speech effect is a cognitive phenomenon observed in psychology, particularly in the study of working memory and attention. •It refers to the finding that the presence of irrelevant background speech or noise can impair a person's ability to perform cognitive tasks that require working memory and concentration.
- 34. Word length effect •The word length effect is a phenomenon observed in cognitive psychology and memory research. •It refers to the finding that it's generally more challenging to remember lists of longer words than lists of shorter words, even when the total number of syllables or characters is the same.
- 35. COGNITIVE AGING • Cognitive aging refers to the natural process of changes in cognitive abilities as a person gets older. These changes can include declines in memory, processing speed, attention, and other mental functions. While some cognitive decline is typical with aging, the extent and rate of decline can vary widely among individuals. Factors like genetics, lifestyle, and overall health can influence cognitive aging. Engaging in activities that stimulate the mind, maintaining a healthy lifestyle, and seeking medical advice, when necessary, can help support cognitive health as people age.
- 36. The cascade model of cognitive ageing • A life course approach to cognitive ageing and cognitive function was also emphasised by the cascade model of cognitive ageing. While it is common to conceptualise the chronology of cognitive ageing from birth to later life, the cascade model suggests that it may be more informative to consider a framework of successful cognitive ageing in relation to the time to death rather than a follow-up from the time of birth. • The model describes primary ageing as a slow decline in mental progressing, often characterised by difficulties in memory (especially with new learning and retention), information processing, language and other aspects of cognitive functions. Secondary ageing represents a more rapid form of deterioration due to a pathological process such as dementia, and refers to a loss of fluid and crystallised cognitive abilities, while tertiary ageing raises the more complex issue of impairments in cognitive performance arising from overall biological devitalisation of the organism before the end of life. Many older individuals demonstrate no apparent cognitive impairment, while others, perhaps most of the aged population, suffer various degrees of cognitive change.
- 37. NEUROPSYCHOLOGICALLY IMPAIRED PATIENTS •Neuropsychologically impaired patients refer to individuals who have experienced damage or dysfunction in their brain, leading to cognitive, emotional, or behavioral difficulties. •These impairments can result from various causes, such as traumatic brain injury, stroke, neurodegenerative diseases like Alzheimer's or Parkinson's, or other neurological conditions.
- 38. Neuropsychologically impaired patients Initial Evaluation and Assessment •Neuropsychological Testing •Medical Examination •Imaging (e.g., MRI, CT scans) •Behavioral Observation
- 39. Neuropsychologically impaired patients Diagnosis and Treatment Planning • Identify Specific Impairments • Develop Individualized Treatment Plan • Involve Multidisciplinary Team (Neuropsychologist, Neurologist, Therapists, etc.)
- 40. Neuropsychologically impaired patients Rehabilitation and Therapy •Cognitive Rehabilitation •Physical and Occupational Therapy •Speech Therapy •Medication Management
- 41. Neuropsychologically impaired patients Progress Monitoring •Regular Assessments •Adjust Treatment Plan as Needed •Track Improvements and Challenges
- 42. Neuropsychologically impaired patients Long-Term Support and Care •Continuation of Therapy and Rehabilitation •Psychological and Emotional Support •Support for Caregivers and Family
- 43. Neuropsychologically impaired patients •These stages involved in the assessment and treatment of neuropsychologically impaired patients, including initial evaluation, diagnosis, rehabilitation, progress monitoring, and long- term support.
- 44. Thank you