Lecture 8: Sensory Processing

Nacho's Intro to Neuro lecture 8 on sensory processing flashcards for studying

What are the main steps of sensory processing?

Stimulus → Transduction by receptor cells → Transmission of action potentials → Interpretation by the brain.

What is an adequate stimulus?

The specific type of stimulus a sensory receptor is most adapted to detect.

What do sensory receptor organs do?

Detect energy or substances and act as filters of the environment.

What is sensory transduction?

Conversion of a stimulus into a change in the electrical potential of a receptor cell.

What is the Doctrine of Specific Nerve Energies?

Each sensory modality has distinct receptors and neural pathways; stimulation of a sensory pathway always results in the same perception.

What are the two main ways intensity is coded in sensory systems?

1. Range fractionation (different thresholds)
2. Number of neurons activated (recruitment).

How is the location of a stimulus encoded?

By the position of activated receptors and their neural pathways.

What is sensory adaptation?

A decrease in receptor response despite continued stimulation.

What is the functional benefit of adaptation?

It helps the brain prioritize new or changing stimuli, avoiding sensory overload.

Difference between tonic and phasic receptors?

Tonic = little adaptation; Phasic = rapid adaptation.

What is bottom-up suppression?

Reducing stimulus intensity before it reaches receptors (e.g., closing eyelids).

What is top-down suppression?

Brain modulates activity in lower sensory centers via descending pathways.

Where do most sensory pathways synapse before reaching the cortex?

The thalamus

What role does the cortex play in sensory suppression?

It can direct the thalamus to emphasize or suppress certain sensory inputs.

What is a receptive field?

The region where a stimulus alters a neuron's firing rate.

What happens to receptive fields as sensory information moves up the pathway?

They become larger and more complex due to integration.

What brain regions are involved in attention?

Posterior parietal lobe and anterior cingulate cortex.

What are two types of attention?

Bottom-up (stimulus-driven) and top-down (goal-driven).

What are interoceptive cues?

Internal signals about the body’s state that influence emotion.

How do subliminal cues affect perception?

Rapid, unconscious processing can influence emotion and judgment (e.g., race, gender, beauty).

What are the steps of sensory processing from stimulus to perception?

1. A stimulus (energy or substance) interacts with sensory receptor organs.

2. Receptor cells transduce the stimulus into electrical signals (receptor potentials).

3. These signals are transmitted as action potentials through sensory neurons.

4. The brain interprets these signals in context to generate perception.

What is the role of sensory receptor organs and cells in sensation?

Sensory receptor organs detect specific types of environmental stimuli. Within these organs, receptor cells convert stimuli into electrical signals, initiating the process of sensory transduction.

What is sensory transduction and where does it occur?

Sensory transduction is the process by which sensory receptor cells convert physical or chemical stimuli into electrical signals (receptor potentials). It occurs at the level of receptor cells within sensory organs.

What is the Doctrine of Specific Nerve Energies and its significance?

Proposed by Johannes Müller, this doctrine states that the nature of a perception is defined by the pathway over which the sensory information is carried, not by the origin of the stimulus. This explains why stimulating the optic nerve always results in visual perception.

How is stimulus intensity coded by sensory systems?

• Range fractionation: Different sensory neurons have different thresholds for firing, allowing detection over a wide intensity range.

• Population coding: As intensity increases, more neurons are recruited.

• Frequency coding: Stronger stimuli can increase the firing rate up to a max of ~1200 action potentials per second.

How is stimulus location encoded in the sensory system?

Stimulus location is coded by the spatial arrangement of activated receptors. In systems like vision and touch, each receptor maps to a specific location. Bilateral systems also use differences in timing or intensity between left and right receptors to localize stimuli.

What is sensory adaptation and why is it important?

Sensory adaptation is the decline in response of a receptor despite continued presence of a stimulus. This helps prevent sensory overload and allows the nervous system to focus on new or changing stimuli, which are more likely to be behaviorally relevant.

Differentiate between tonic and phasic receptors

• Tonic receptors respond continuously with little adaptation (e.g., pain receptors).

• Phasic receptors adapt quickly and respond mainly to changes in stimulus (e.g., touch receptors).

Describe bottom-up vs. top-down sensory suppression strategies.

• Bottom-up suppression: Sensory input is physically reduced before reaching receptors (e.g., closing eyelids to reduce light).

• Top-down suppression: Brain actively modulates lower sensory centers via descending signals to enhance or inhibit specific sensory inputs.

What is the general pathway of sensory information to the brain?

Each sensory modality has its own pathway that transmits information from peripheral receptors → spinal cord/brainstem → thalamus → primary sensory cortex → secondary sensory cortex.

What role does the thalamus play in sensory processing?

The thalamus relays and filters sensory signals (except for smell) before they reach the cortex. It also plays a role in attention and top-down suppression by prioritizing certain inputs over others.

What is a receptive field and how does it change along the sensory pathway?

A receptive field is the specific region where a stimulus alters a neuron's firing rate. As sensory information ascends, neurons integrate signals from multiple lower-level inputs, resulting in larger, more complex receptive fields.

What is the organization of primary and secondary sensory cortices?

Each modality has a primary cortex (e.g., primary visual cortex) where basic features are processed, and a secondary cortex where more complex integration and interpretation occur.

How is attention implemented in the brain?

Attention enhances the processing of selected stimuli through both bottom-up and top-down mechanisms. The posterior parietal lobe manages spatial attention, while the anterior cingulate cortex is involved in emotional relevance and discomfort (e.g., pain processing).

What are interoceptive cues and their relevance to emotion?

Interoceptive cues are internal body signals (like heart rate, respiration) that contribute to emotional experience. Brain regions like the insular cortex, anterior cingulate, and amygdala process these signals and influence emotions, supporting theories like the James-Lange theory.

What are examples of subliminal or unconscious cues that influence behavior?

Stimuli like race, gender, dominance, and beauty can affect perception before conscious awareness. For instance, faces from another race may activate the amygdala, and beauty can bias judgments via the orbitofrontal cortex, which is associated with reward and moral evaluation.

Beauty

Associated with kinder, smarter, and more honest people; activates medial orbitofrontal cortex which is
responsible for both determining beauty and the goodness of behavior

According to James-Lang theory:

Internal cues directly lead to emotional changes

Interoceptive cues is information about the body’s internal state. They can:

Influence emotion and guide our responses to external stimuli or situations.

What are the six aspects of sensory processing?

1. Coding

2. Adaptation

3. Suppression

4. Pathways

5. Receptive Fields

6. Attention